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− | <object data="https://static.igem.org/mediawiki/2017/c/c6/T--SDU-Denmark--wiki-explained.svg" type="image/svg+xml"> | + | <object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/c/c6/T--SDU-Denmark--wiki-explained.svg" type="image/svg+xml"> |
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<h3><span class="highlighted">Abstract</span></h3> | <h3><span class="highlighted">Abstract</span></h3> | ||
<hr> | <hr> | ||
− | <p><span class="highlighted">With the PowerLeaf, iGEM SDU is introducing a novel solution for long-term storage of solar energy, becoming an alternative to solar cells</span>, without using environmentally harmful resources. We aim to accomplish this through the creation of a device visually shaped to resemble a leaf, | + | <p><span class="highlighted">With the PowerLeaf, iGEM SDU is introducing a novel solution for long-term storage of solar energy, thus becoming an alternative to solar cells</span>, without using environmentally harmful resources. We aim to accomplish this through the creation of a device visually shaped to resemble a plant leaf, thereby providing a nature-in-city ambience. The team invested heavily in public engagement and collaborations to investigate how the device hypothetically could be implemented into an urban environment. From a technical perspective, <span class="highlighted">the bacterial solar battery is composed of an energy storing unit and an energy converting unit</span>. The energy storing unit is defined by a genetically engineered <i>Escherichia coli</i>, that fixates carbon dioxide into the chemically stable polymer cellulose, while the energy converting unit uses genetically engineered <i> Escherichia coli</i> to consume the stored cellulose. Electrons retrieved from this process, are transferred to an anode by optimised nanowires, thereby creating an electrical current. Last but not least, the energy storing unit has a light-dependent system, which activates dormancy during nighttime to reduce energy lost by metabolism. |
</p> | </p> | ||
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<div class="col-md-5 col-sm-6 verticalAlignColumnsAbstract"> | <div class="col-md-5 col-sm-6 verticalAlignColumnsAbstract"> | ||
<div id="sketchAbstract"> | <div id="sketchAbstract"> | ||
− | <object id="sketchbook" data="https://static.igem.org/mediawiki/2017/0/08/T--SDU-Denmark--sketchbook_and_pen.svg" type="image/svg+xml"> | + | <object id="sketchbook" class="highlighted-image" data="https://static.igem.org/mediawiki/2017/0/08/T--SDU-Denmark--sketchbook_and_pen.svg" type="image/svg+xml"> |
</object> | </object> | ||
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− | <div class="row" style="margin-top: | + | <div class="row" style="padding-top: 180px; margin-top:-110px; margin-bottom:110px;" id="igem-goes-green"> |
<div class="col-xs-1 verticalAlignColumnsAbstract"></div> | <div class="col-xs-1 verticalAlignColumnsAbstract"></div> | ||
<div class="col-xs-2 verticalAlignColumnsAbstract" style="text-align:center;"><a href="https://www.ingenco2.dk/crt/dispcust/c/4676/l/1" target="_blank"><img class="highlighted-image" src="https://static.igem.org/mediawiki/2017/9/9c/T--SDU-Denmark--co2-neutral-website.png" width="60%"/></a></div> | <div class="col-xs-2 verticalAlignColumnsAbstract" style="text-align:center;"><a href="https://www.ingenco2.dk/crt/dispcust/c/4676/l/1" target="_blank"><img class="highlighted-image" src="https://static.igem.org/mediawiki/2017/9/9c/T--SDU-Denmark--co2-neutral-website.png" width="60%"/></a></div> | ||
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<div class="col-md-8 col-xs-10 margin-bottom-200 margin-top-50"> | <div class="col-md-8 col-xs-10 margin-bottom-200 margin-top-50"> | ||
− | <p><span class="largeFirstLetter">W</span>elcome to our wiki! <span class="highlighted">We are the iGEM team from the University of Southern Denmark</span> | + | <p><span class="largeFirstLetter">W</span>elcome to our wiki! <span class="highlighted">We are the iGEM team from the University of Southern Denmark</span> and we have been waiting in great anticipation for the chance to tell you our story. |
<br> | <br> | ||
− | Our adventure began with a meeting between strangers from eight different studies. Despite our different backgrounds, we had one thing in common; a shared interest in synthetic biology. Soon after this first meeting, we were herded off to a weekend in a cottage - far away from our regular lives. The cottage was a place to bond and discuss project ideas. It immediately became apparent that <span class="highlighted">being an interdisciplinary team was going to be our strength</span> | + | Our adventure began with a meeting between strangers from eight different studies. Despite our different backgrounds, we had one thing in common; a shared interest in synthetic biology. Soon after this first meeting, we were herded off to a weekend in a cottage - far away from our regular lives. The cottage was a place to bond and discuss project ideas. It immediately became apparent that <span class="highlighted">being an interdisciplinary team was going to be our strength</span> as each member had unique qualities that enabled them to efficiently tackle different aspects of the iGEM competition. So, we made it our goal to take advantage of these qualities. |
<br> | <br> | ||
− | We decided to make a proof-of-concept project. Specifically, we wanted to use <span class="highlighted">bacteria as a novel and greener solution for solar energy storage</span>. This project was later dubbed the PowerLeaf – | + | We decided to make a proof-of-concept project. Specifically, we wanted to use <span class="highlighted">bacteria as a novel and greener solution for solar energy storage</span>. This project was later dubbed the PowerLeaf – A Bacterial Solar Battery. |
<br> | <br> | ||
Since it is a one-page wiki, you can <span class="highlighted">just keep on scrolling, and you will be taken on a journey through our iGEM experience</span>. | Since it is a one-page wiki, you can <span class="highlighted">just keep on scrolling, and you will be taken on a journey through our iGEM experience</span>. | ||
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<div class="col-xs-8 verticalAlignColumns padding0 left right"> | <div class="col-xs-8 verticalAlignColumns padding0 left right"> | ||
<p class="P-Larger"><b><span class="highlighted">Bronze Medal Requirements</span></b><br class="shortBreak"> | <p class="P-Larger"><b><span class="highlighted">Bronze Medal Requirements</span></b><br class="shortBreak"> | ||
− | <p><b>Register and | + | <p><b>Register and Attend</b> – Our team applied on the 30<sup>th</sup> of March 2017 and got accepted the 4<sup>th</sup> of May 2017. We had an amazing summer and are looking forward to attend the Giant Jamboree!<br> |
− | <b>Meet all the | + | <b>Meet all the Deliverables Requirements</b> – You are reading the team wiki now, so that is one cat in the bag. You can find all attributions made to the project in the <a href="https://2017.igem.org/Team:SDU-Denmark#attributions" target="_blank">Credits section</a> of the wiki. The team poster and team presentation are ready to be presented at the Giant Jamboree. We also filled the <a href="https://2017.igem.org/Safety/Final_Safety_Form?team_id=2449" target="_blank">safety form</a>, the <a href="https://igem.org/2017_Judging_Form?id=2449" target="_blank">judging form</a> and all our <a href="http://parts.igem.org/cgi/dna_transfer/batch_list.cgi?group_id=2951" target="_blank">parts</a> were registered and submitted.<br> |
− | <b>Clearly | + | <b>Clearly State the Attributions</b> – All attributions made to our project have been clearly credited in the <a href="https://2017.igem.org/Team:SDU-Denmark#attributions" target="_blank">Credits section</a>.<br> |
− | <b>Improve and/or | + | <b>Improve and/or Characterise an Existing Biobrick Part or Device</b> – The characterisation of the OmpR-regulated promoter <a href="http://parts.igem.org/Part:BBa_R0082" target="_blank">BBa_R0082</a> was improved, as the level of noise was studied on different vectors. <br class="miniBreak"> |
Induction and inhibition of the pBAD promoter, <a href="http://parts.igem.org/Part:BBa_I0500" target="_blank">BBa_I0500</a>, were studied, whereby the characterisation of this part was improved. <br class="miniBreak"> | Induction and inhibition of the pBAD promoter, <a href="http://parts.igem.org/Part:BBa_I0500" target="_blank">BBa_I0500</a>, were studied, whereby the characterisation of this part was improved. <br class="miniBreak"> | ||
Furthermore, we characterized if the periplasmic beta-glucosidase could make <i>E. coli</i> live on cellobiose in fluid medium <a href="http://parts.igem.org/Part:BBa_K523014" target="_blank">BBa_K523014</a>, submitted by the <a href="https://2011.igem.org/Team:Edinburgh" target="_blank">2011 iGEM Edinburgh Team</a>. | Furthermore, we characterized if the periplasmic beta-glucosidase could make <i>E. coli</i> live on cellobiose in fluid medium <a href="http://parts.igem.org/Part:BBa_K523014" target="_blank">BBa_K523014</a>, submitted by the <a href="https://2011.igem.org/Team:Edinburgh" target="_blank">2011 iGEM Edinburgh Team</a>. | ||
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<div class="col-xs-8 verticalAlignColumns padding0 left"> | <div class="col-xs-8 verticalAlignColumns padding0 left"> | ||
<p class="P-Larger"><b><span class="highlighted">Silver Medal Requirements</span></b></p><br class="shortBreak"> | <p class="P-Larger"><b><span class="highlighted">Silver Medal Requirements</span></b></p><br class="shortBreak"> | ||
− | <p><b>Validated | + | <p><b>Validated Part/Contribution</b> – We created the part <a href="http://parts.igem.org/Part:BBa_K2449004" target="_blank">BBa_K2449004</a>, containing a cellobiose phosphorylase. This enzyme enables <i>Escherichia coli</i> to survive on cellobiose, which we validated by growth experiments. The data obtained in these experiments are presented in the <a href="https://2017.igem.org/Team:SDU-Denmark#demonstration-and-results" target="_blank">Demonstration & Results section</a>.<br> |
− | <b>Collaboration</b> – We have collaborated with several teams throughout our project by taking part in discussions, meetups, and answering questionnaires - we even hosted our first meetup for our fellow Danish iGEM teams. You will get to read all about this in the <a href="https://2017.igem.org/Team:SDU-Denmark#collaborations" target="_blank"> | + | <b>Collaboration</b> – We have collaborated with several teams throughout our project by taking part in discussions, meetups, and answering questionnaires - we even hosted our first meetup for our fellow Danish iGEM teams. You will get to read all about this in the <a href="https://2017.igem.org/Team:SDU-Denmark#collaborations" target="_blank">Credits section</a>.<br> |
− | <b>Human Practices</b> – Our philosopher, historian, and biologist have discussed the <a href="https://2017.igem.org/Team:SDU-Denmark#bioethics" target="_blank">ethical and educational aspects</a> of our project in great detail. In extension to their work, we have been working extensively with <a href="https://2017.igem.org/Team:SDU-Denmark#education-and-public-engagement" target="_blank">public engagement | + | <b>Human Practices</b> – Our philosopher, historian, and biologist have discussed the <a href="https://2017.igem.org/Team:SDU-Denmark#bioethics" target="_blank">ethical and educational aspects</a> of our project in great detail. In extension to their work, we have been working extensively with <a href="https://2017.igem.org/Team:SDU-Denmark#education-and-public-engagement" target="_blank">education and public engagement </a>.<br> |
</p> | </p> | ||
</div> | </div> | ||
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<p><b>Integrated Human Practices</b> – Regarding the <href="https://2017.igem.org/Team:SDU-Denmark#integrated-practices" target="_blank">development and implementation</a> of the device, we reached out to and remained in contact with city planners from our hometown throughout our project. This regarded advice and conversations on anything from the possible design, value, safety, use, placement, and plastic type of our device. We also made sure to integrate the findings of said conversations into our overall project. Last but not least, we focused on demonstrating this process on our wiki in order to inspire future iGEM teams. <br> | <p><b>Integrated Human Practices</b> – Regarding the <href="https://2017.igem.org/Team:SDU-Denmark#integrated-practices" target="_blank">development and implementation</a> of the device, we reached out to and remained in contact with city planners from our hometown throughout our project. This regarded advice and conversations on anything from the possible design, value, safety, use, placement, and plastic type of our device. We also made sure to integrate the findings of said conversations into our overall project. Last but not least, we focused on demonstrating this process on our wiki in order to inspire future iGEM teams. <br> | ||
− | <b>Model | + | <b>Model Your Project</b> – Through extensive <a href="https://2017.igem.org/Team:SDU-Denmark#modelling" target="_blank">modelling</a>, we have learned that it is possible to regulate bacterial dormancy. However, the modelling showed that it would be inadequate to only regulate the toxin RelE, as this would make the bacteria unable to exit dormancy. To regulate dormancy properly, would also require tight regulation of the antitoxin RelB. This information was used to shape the entire approach of the light-dependent dormancy system.<br> |
</p> | </p> | ||
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<p> </p> | <p> </p> | ||
</div> | </div> | ||
− | <div class="row"><div class="col-xs-12 | + | <div class="row"><div class="col-xs-12"><div class="coverPicture" style="text-align:center;"><object class="highlighted-image" style="width:100%; border-radius: 5px;" data="https://static.igem.org/mediawiki/2017/9/9c/T--SDU-Denmark--sustainability.svg" type="image/svg+xml"></object></div></div></div> |
</div> | </div> | ||
<div class="row"><div class="col-xs-12"> | <div class="row"><div class="col-xs-12"> | ||
− | <p class="P-Larger"><span class="highlighted"><b>A Global | + | <p class="P-Larger"><span class="highlighted"><b>A Global Challenge</b></span></p> |
<p>In the world of today, <span class="highlighted">it is becoming increasingly important to ensure a sustainable future</span><span class="reference"><span class="referencetext"><a target="blank" href="hhttp://wwwoecdorg/greengrowth/MATERIAL%20RESOURCES,%20PRODUCTIVITY%20AND%20THE%20ENVIRONMENT_key%20findingspdf"> Green Growth Papers (Myriam Linster). Material Resources, Productivity and the Environment. 2013.</a></span></span>. Not just for our generation, but especially for the generations to come, as their possibilities should not be limited by our choices. | <p>In the world of today, <span class="highlighted">it is becoming increasingly important to ensure a sustainable future</span><span class="reference"><span class="referencetext"><a target="blank" href="hhttp://wwwoecdorg/greengrowth/MATERIAL%20RESOURCES,%20PRODUCTIVITY%20AND%20THE%20ENVIRONMENT_key%20findingspdf"> Green Growth Papers (Myriam Linster). Material Resources, Productivity and the Environment. 2013.</a></span></span>. Not just for our generation, but especially for the generations to come, as their possibilities should not be limited by our choices. | ||
− | Our solution, is the development of a green and renewable technology, which offers new advantages to the field of sustainable energy. <span class="highlighted">There are currently certain limitations to the existing options for renewable energy</span>, namely the intermittency and the diluteness problem <span class="reference"><span class="referencetext"><a target="blank" href=" https://www.researchgate.net/publication/279212503_Global_Lithium_Resources_and_Sustainability_Issues"> Alexandre Chagnes JS. Global Lithium Resources and Sustainability Issues. Lithium Process Chemistry: Elsevier; June 2015. p. pp.1-40.</a></span></span>. The intermittency problem describes the discontinuous energy production, along with inefficient storage. On the other hand, the diluteness problem is characterised as the resource-demanding production of technical devices, such as solar cells and batteries. This means that a lack of resources eventually would eliminate the current forms of green technology. As such, we need to <span class="highlighted">introduce a new and sustainable approach to green energy</span> to ensure the continuation of our beautiful world for the coming generations. | + | Our solution, is the development of a green and renewable technology, which offers new advantages to the field of sustainable energy. <span class="highlighted">There are currently certain limitations to the existing options for renewable energy</span>, namely the intermittency and the diluteness problem <span class="reference"><span class="referencetext"><a target="blank" href=" https://www.researchgate.net/publication/279212503_Global_Lithium_Resources_and_Sustainability_Issues"> Alexandre Chagnes JS. Global Lithium Resources and Sustainability Issues. Lithium Process Chemistry: Elsevier; June 2015. p. pp.1-40.</a></span></span>. The intermittency problem describes the discontinuous energy production, along with inefficient storage. On the other hand, the diluteness problem is characterised as the resource-demanding production of technical devices, such as solar cells and batteries. This means that a lack of resources eventually would eliminate some of the current forms of green technology. As such, we need to <span class="highlighted">introduce a new and sustainable approach to green energy</span> to ensure the continuation of our beautiful world for the coming generations. |
</p> | </p> | ||
<br class="noContent"> | <br class="noContent"> | ||
<br class="noContent"> | <br class="noContent"> | ||
<p class="P-Larger"><span class="highlighted"><b>In a Local Environment</b></span></p> | <p class="P-Larger"><span class="highlighted"><b>In a Local Environment</b></span></p> | ||
− | <p>We are a team of young adults raised with an awareness of climate changes and the potential limitations to our ways of life. As a generation that appreciates open source and shared information, we have been encouraged to constantly challenge the ideas of yesterday. With this in mind, <span class="highlighted">we decided the best solution to the eventual energy crisis would be to seek out experts and the general public, even children, in order to rethink the current notion</span> | + | <p>We are a team of young adults raised with an awareness of climate changes and the potential limitations to our ways of life. As a generation that appreciates open source and shared information, we have been encouraged to constantly challenge the ideas of yesterday. With this in mind, <span class="highlighted">we decided the best solution to the eventual energy crisis would be to seek out experts and the general public, even children, in order to rethink the current notion</span> that the only way to save our planet, is to compromise our living standards. |
<br> | <br> | ||
− | Fortunately, we learned through interaction with local agents that a great deal of people share our belief | + | Fortunately, we learned through interaction with local agents that a great deal of people share our belief: that <span class="highlighted">we ought to pursue the development of low energy cities with a high quality of life</span>. In fact, we even discovered that our own hometown Odense wants to be the greenest, most renewable city in Denmark by 2050 <span class="reference"><span class="referencetext"><a target="blank" href="https://www.odense.dk/borger/miljoe-og-affald/klima">Odense Municipality’s website, regarding their politics on the current climate changes.</a></span></span>. |
<br> | <br> | ||
− | In the pursuit of this goal | + | In the pursuit of this goal <span class="highlighted">we rose to the challenge of creating a truly green solution</span>, which would provide an environmental friendly source of energy. |
<br> | <br> | ||
− | <span class="highlighted">Please keep scrolling if you wish to read more about our solution</span>, or go straight to <a href= | + | <span class="highlighted">Please keep scrolling if you wish to read more about our solution</span>, or go straight to <a href="https://2017.igem.org/Team:SDU-Denmark#bioethics" target="_blank">bioethics</a> if you are curious why we not only <i>could</i>, but <i>ought</i> to do something about the current and forthcoming energy crisis. |
</p> | </p> | ||
<br class="noContent"> | <br class="noContent"> | ||
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<div class="row"><div class="col-xs-12"> | <div class="row"><div class="col-xs-12"> | ||
− | + | <p><span class="highlighted">The vision for our bacterial solar battery is to combine two aspects, energy storage and energy conversion, by which we will produce a new and improved type of solar battery. We have named this vision The PowerLeaf</span>. The PowerLeaf consist of two chambers that will be referred to as <i>the outer chamber or energy storing unit</i> and <i>the inner chamber or energy converting unit</i>.</p> | |
− | <p><span class="highlighted">The vision for our bacterial solar battery is to combine two aspects | + | <ul class="list" style="margin-top:15px;"> |
− | <ul class="list"> | + | |
<li><span class="highlighted">The energy storing unit comprises genetically engineered <i>Escherichia coli</i> (<i>E. coli</i>), which uses solar energy for ATP production to fixate carbon dioxide into the chemically stable polymer cellulose. <span class="highlighted"> The cellulose works as the battery</span> in the PowerLeaf, storing the chemical energy. A light sensing system activates dormancy during nighttime, leading to a reduced loss of energy through metabolism.</span></li> | <li><span class="highlighted">The energy storing unit comprises genetically engineered <i>Escherichia coli</i> (<i>E. coli</i>), which uses solar energy for ATP production to fixate carbon dioxide into the chemically stable polymer cellulose. <span class="highlighted"> The cellulose works as the battery</span> in the PowerLeaf, storing the chemical energy. A light sensing system activates dormancy during nighttime, leading to a reduced loss of energy through metabolism.</span></li> | ||
<li><span class="highlighted">The energy converting unit uses genetically engineered <i>E. coli</i> to consume the stored cellulose by using an inducible switch. Retrieved electrons are transferred by extracellular electron carriers to an anode, resulting in an electrical current.</span></li> | <li><span class="highlighted">The energy converting unit uses genetically engineered <i>E. coli</i> to consume the stored cellulose by using an inducible switch. Retrieved electrons are transferred by extracellular electron carriers to an anode, resulting in an electrical current.</span></li> | ||
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<div class="col-md-8 col-xs-10 margin-bottom-200 margin-top-50"> | <div class="col-md-8 col-xs-10 margin-bottom-200 margin-top-50"> | ||
− | <p><span class=" | + | <p><span class="highlighted">Our device is composed of two units, an energy storing unit and an energy converting unit</span>, each divided into systems, all of which have been given a symbol to help you navigate throughout the wiki.</b></p> |
− | < | + | |
+ | <p><span class="highlighted"><b>Energy Storing Unit</b></span></p> | ||
<ul class="project-outline"> | <ul class="project-outline"> | ||
− | <li class="project-outline-checked"><p> | + | <li class="project-outline-checked"><p><span class="highlighted">Dormancy System</span></p></li> |
− | <li class="project-outline-crossed"><p>Carbon | + | <li class="project-outline-crossed"><p><span class="highlighted">Carbon Fixation</span></p></li> |
− | <li class="project-outline-crossed"><p>Cellulose | + | <li class="project-outline-crossed"><p><span class="highlighted">Cellulose Biosynthesis</span></p></li> |
</ul><br> | </ul><br> | ||
− | <p><b>Energy | + | <p><span class="highlighted"><b>Energy Converting Unit</b></span></p> |
<ul class="project-outline"> | <ul class="project-outline"> | ||
− | <li class="project-outline-checked"><p>Breakdown of | + | <li class="project-outline-checked"><p><span class="highlighted">Breakdown of Cellulose</span></p></li> |
− | <li class="project-outline-checked"><p>Extracellular | + | <li class="project-outline-checked"><p><span class="highlighted">Extracellular Electron Transfer</span></p></li> |
</ul> | </ul> | ||
− | <p> | + | <p>In the <a href="https://2017.igem.org/Team:SDU-Denmark#project-design" target="_blank">Project Design section</a>, you will first be given a short introduction to the background, followed by the approach of that system, before you move on to the next system. Once you reach the next section of the wiki, <a href="https://2017.igem.org/Team:SDU-Denmark#demonstration-and-results" target="_blank">Demonstration & Results</a>, you will be guided through the performed experiments and the derived conclusions. To make things easier for you, we have continued to use the above symbols throughout our wiki. |
</p> | </p> | ||
</div> | </div> | ||
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− | |||
</div> | </div> | ||
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<div class="row margin-bottom-75 padding-top-125" id="project-design-dormancy-system" style="margin-top:-125px;"><div class="col-xs-12"> | <div class="row margin-bottom-75 padding-top-125" id="project-design-dormancy-system" style="margin-top:-125px;"><div class="col-xs-12"> | ||
<div class"row"><div class="project-design-headline"><object class="highlighted-image project-design-icon" data="https://static.igem.org/mediawiki/2017/7/7c/T--SDU-Denmark--zzz-icon.svg" type="image/svg+xml"></object><h2>Dormancy System</h2></div></div> | <div class"row"><div class="project-design-headline"><object class="highlighted-image project-design-icon" data="https://static.igem.org/mediawiki/2017/7/7c/T--SDU-Denmark--zzz-icon.svg" type="image/svg+xml"></object><h2>Dormancy System</h2></div></div> | ||
+ | |||
<div style="text-align:center;"><p><span class="reference-2">Project Overview<span class="referencetext-2"><object data="https://static.igem.org/mediawiki/2017/2/24/T--SDU-Denmark--project-overview-dormancy.svg" style="width:100%;" type="image/svg+xml"></object></span></span></p></div><br> | <div style="text-align:center;"><p><span class="reference-2">Project Overview<span class="referencetext-2"><object data="https://static.igem.org/mediawiki/2017/2/24/T--SDU-Denmark--project-overview-dormancy.svg" style="width:100%;" type="image/svg+xml"></object></span></span></p></div><br> | ||
− | <p class="P-Larger"><b> | + | <p class="P-Larger"><b>Introduction</b></p><br> |
− | <p>Cyanobacteria contain signal transduction systems, thereby making them capable of <span class="highlighted">sensing and responding to light</span> <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3732953/">Bussell AN, Kehoe DM. Control of a four-color sensing photoreceptor by a two-color sensing photoreceptor reveals complex light regulation in cyanobacteria. Proceedings of the National Academy of Sciences of the United States of America. 2013;110(31):12834-9.</a></span></span>. This ability gives the organisms the opportunity | + | <p>Cyanobacteria contain signal transduction systems, thereby making them capable of <span class="highlighted">sensing and responding to light</span> <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3732953/">Bussell AN, Kehoe DM. Control of a four-color sensing photoreceptor by a two-color sensing photoreceptor reveals complex light regulation in cyanobacteria. Proceedings of the National Academy of Sciences of the United States of America. 2013;110(31):12834-9.</a></span></span>. This ability gives the organisms the opportunity to <span class="highlighted">adapt and optimize their metabolism to a circadian rhythm</span>. Photoreceptors in the plasma membrane, of which phytochromes are especially abundant and well described, are responsible for this property <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/11145881">Vierstra RD, Davis SJ. Bacteriophytochromes: new tools for understanding phytochrome signal transduction. Seminars in cell & developmental biology. 2000;11(6):511-21.</a></span></span>. In 2004, the <a href="https://2004.igem.org/austin.cgi" target="_blank">UT Austin iGEM team</a> made a light response system consisting of a photoreceptor combined with an intracellular indigenous regulator system <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/16306980">Levskaya A, Chevalier AA, Tabor JJ, Simpson ZB, Lavery LA, Levy M, et al. Synthetic biology: engineering Escherichia coli to see light. Nature. 2005;438(7067):441-2.</a></span></span>. EnvZ and OmpR make up the two-component system naturally found in <i>E. coli</i>. The photoreceptor known as Cph1 was isolated from the cyanobacteria <i>Synechocytis</i> PCC6803. Cph1 has functional combination sites, which combined with the kinase EnvZ form a two-domain receptor, known as Cph8. Activation of Cph8 is mediated by the chromophore phycocyanobilin, PCB, that is <span class="highlighted">sensitive to red light</span> with maximal absorbance at 662 nm <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/11532008">Lamparter T, Esteban B, Hughes J. Phytochrome Cph1 from the cyanobacterium Synechocystis PCC6803. Purification, assembly, and quaternary structure. European journal of biochemistry. 2001;268(17):4720-30.</a></span></span>. |
<br> | <br> | ||
− | <span class="highlighted">When not exposed to light</span>, PCB activates the phytochrome Cph1, | + | <span class="highlighted">When not exposed to light</span>, PCB activates the phytochrome Cph1, thus promoting kinase activity through the EnvZ kinase. When the transcription factor OmpR is phosphorylated by EnvZ, <span class="highlighted">expression of genes regulated by the OmpR-regulated promoter is initiated. Excitation of PCB by red light</span> results in a situation where the transcription factor OmpR is not regulated. The absence of phosphorylated OmpR leads to no activation of the OmpR-regulated promoter, thereby <span class="highlighted">preventing gene expression</span>. |
</p><br> | </p><br> | ||
<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/6/6f/T--SDU-Denmark--light-sensing-cph8.svg" type="image/svg+xml" style="width:100%;"></object></div> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/6/6f/T--SDU-Denmark--light-sensing-cph8.svg" type="image/svg+xml" style="width:100%;"></object></div> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 1.</b> Left: Red light activates PCB, which in turn inactivates the photoreceptor complex Cph8, preventing gene expression from the OmpR-regulated promoter. Right: In absence of light, PCB is inactive, which enables the Cph8 to phosphorylate the transcription factor OmpR. This promotes gene expression from the OmpR-regulated promoter.</p></div><br class="noContent"> |
<br><p> | <br><p> | ||
− | + | The <span class="highlighted">photocontrol device can be used to regulate a toxin-antitoxin system</span>, enabling the implementation of a light-dependent dormancy system. A toxin-antitoxin system is composed of two gene products, a cytotoxin and an antitoxin, the latter which neutralises the the toxic effect caused by the toxin. | |
+ | In <i>E. coli</i> K-12 the cytotoxin RelE and antitoxin RelB comprise such a system <span class="reference"><span class="referencetext"><a target="blank" href=" https://www.ncbi.nlm.nih.gov/pubmed/9767574">Gotfredsen M, Gerdes K. The Escherichia coli relBE genes belong to a new toxin-antitoxin gene family. Molecular microbiology. 1998;29(4):1065-76.</a></span></span>. Expression of the <span class="highlighted">cytotoxin RelE inhibits translation in the cells</span>, due to its ability to cleave mRNA found in the A-site of the ribosome. <span class="highlighted">RelB neutralises the toxic effect of RelE</span> through interaction between the two proteins. Whether the cell lies dormant in response to expression of RelE depends on the ratio of antitoxin RelB and RelE present in the cell. Several studies have shown that RelB and RelE form a complex with RelB:RelE stoichiometry of 2:1 <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/19747491">Overgaard M, Borch J, Gerdes K. RelB and RelE of Escherichia coli form a tight complex that represses transcription via the ribbon-helix-helix motif in RelB. Journal of molecular biology. 2009;394(2):183-96.</a></span></span><span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/18532983">Overgaard M, Borch J, Jorgensen MG, Gerdes K. Messenger RNA interferase RelE controls relBE transcription by conditional cooperativity. Molecular microbiology. 2008;69(4):841-57.</a></span></span>. When the RelB:RelE stoichiometric-ratio is lowered to 1:1, studies show that RelB is not able to protect the cells against the RelE-caused translational inhibition <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/18532983">Overgaard M, Borch J, Jorgensen MG, Gerdes K. Messenger RNA interferase RelE controls relBE transcription by conditional cooperativity. Molecular microbiology. 2008;69(4):841-57.</a></span></span>. For further information about the light-dependent dormancy system, <span class="btn-link btn-lg" data-toggle="modal" data-target="#light-sensing-system-theory">read here</span>. | ||
</p><br> | </p><br> | ||
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Several two-component signal transduction systems evolved in <i>E. coli</i> enables it to respond to various external conditions, such as osmotic stress, lack of metabolites and other external stress factors. Nothing indicates that light initiates such a two-component signal transduction pathway in wild type <i>E. coli</i> <span class="reference"><span class="referencetext"><a target="blank" href="http://www.microbiologyresearch.org/docserver/fulltext/micro/22/1/mic-22-1-113.pdf?expires=1507966841&id=id&accname=guest&checksum=574A5913441399B962AA6A4F887C733E">Alper T, Gillies NE. The relationship between growth and survival after irradiation of Escherichia coli strain B and two resistant mutants. Journal of general microbiology. 1960;22:113-28.</a></span></span>. The <a href="https://2004.igem.org/austin.cgi" target="_blank">UT Austin iGEM 2004 team</a> applied the light sensing property of phototrophs to an <i>E. coli</i>. By aligning different phytochromes with the intrinsic kinase EnvZ from <i>E. coli</i> they revealed a way to create a two-component system consisting of a photoreceptor with an intracellular indigenous regulator system found in <i>E. coli</i>. By establishing this system the bacteria acquired the ability to respond to red light <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/16306980">Levskaya A, Chevalier AA, Tabor JJ, Simpson ZB, Lavery LA, Levy M, et al. Synthetic biology: engineering Escherichia coli to see light. Nature. 2005;438(7067):441-2.</a></span></span>. The photoreceptor from phytochrome known as Cph1 was isolated from the cyanobacteria <i>Synechocytis</i> PCC6803. Cph1 has a fusion site, which can be used to combine it with the kinase EnvZ, from the EnvZ-OmpR kinase-regulator system, to form a two-domain receptor known as Cph8. The chromophore phycocyanobilin (PCB) absorbs light in the red region with maximal absorbance at 662 nm <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/11532008">Lamparter T, Esteban B, Hughes J. Phytochrome Cph1 from the cyanobacterium Synechocystis PCC6803. Purification, assembly, and quaternary structure. European journal of biochemistry. 2001;268(17):4720-30.</a></span></span>. When heterogeneously expressed in <i>E. coli</i>, it can, in combination with the light receptor Cph8, be used to form a light-sensitive circuit, making <i>E. coli</i> able to respond to red light <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3053042/">abor JJ, Levskaya A, Voigt CA. Multichromatic control of gene expression in Escherichia coli. Journal of molecular biology. 2011;405(2):315-324. </a></span></span>. | Several two-component signal transduction systems evolved in <i>E. coli</i> enables it to respond to various external conditions, such as osmotic stress, lack of metabolites and other external stress factors. Nothing indicates that light initiates such a two-component signal transduction pathway in wild type <i>E. coli</i> <span class="reference"><span class="referencetext"><a target="blank" href="http://www.microbiologyresearch.org/docserver/fulltext/micro/22/1/mic-22-1-113.pdf?expires=1507966841&id=id&accname=guest&checksum=574A5913441399B962AA6A4F887C733E">Alper T, Gillies NE. The relationship between growth and survival after irradiation of Escherichia coli strain B and two resistant mutants. Journal of general microbiology. 1960;22:113-28.</a></span></span>. The <a href="https://2004.igem.org/austin.cgi" target="_blank">UT Austin iGEM 2004 team</a> applied the light sensing property of phototrophs to an <i>E. coli</i>. By aligning different phytochromes with the intrinsic kinase EnvZ from <i>E. coli</i> they revealed a way to create a two-component system consisting of a photoreceptor with an intracellular indigenous regulator system found in <i>E. coli</i>. By establishing this system the bacteria acquired the ability to respond to red light <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/16306980">Levskaya A, Chevalier AA, Tabor JJ, Simpson ZB, Lavery LA, Levy M, et al. Synthetic biology: engineering Escherichia coli to see light. Nature. 2005;438(7067):441-2.</a></span></span>. The photoreceptor from phytochrome known as Cph1 was isolated from the cyanobacteria <i>Synechocytis</i> PCC6803. Cph1 has a fusion site, which can be used to combine it with the kinase EnvZ, from the EnvZ-OmpR kinase-regulator system, to form a two-domain receptor known as Cph8. The chromophore phycocyanobilin (PCB) absorbs light in the red region with maximal absorbance at 662 nm <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/11532008">Lamparter T, Esteban B, Hughes J. Phytochrome Cph1 from the cyanobacterium Synechocystis PCC6803. Purification, assembly, and quaternary structure. European journal of biochemistry. 2001;268(17):4720-30.</a></span></span>. When heterogeneously expressed in <i>E. coli</i>, it can, in combination with the light receptor Cph8, be used to form a light-sensitive circuit, making <i>E. coli</i> able to respond to red light <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3053042/">abor JJ, Levskaya A, Voigt CA. Multichromatic control of gene expression in Escherichia coli. Journal of molecular biology. 2011;405(2):315-324. </a></span></span>. | ||
<br> | <br> | ||
− | In situations where no red light is present, the photoreceptor PCB activates the phytochrome Cph1, thereby promoting kinase activity through the EnvZ kinase, illustrated in figure | + | In situations where no red light is present, the photoreceptor PCB activates the phytochrome Cph1, thereby promoting kinase activity through the EnvZ kinase, illustrated in figure 1. When the transcription factor OmpR is phosphorylated by EnvZ, expression of genes controlled by the OmpR-regulated promoter is initiated. Excitation of the PCB by red light, results in a situation, where EnvZ will not be able to phosphorylate the transcription factor OmpR. The lack of phosphorylated OmpR leads to no activation of the OmpR-regulated promoter, thereby preventing gene expression by this promoter.<br> |
<br class="noContent"> | <br class="noContent"> | ||
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<b>RelE and RelB Comprise a Toxin-Antitoxin System in <i>E. coli</i></b><br> | <b>RelE and RelB Comprise a Toxin-Antitoxin System in <i>E. coli</i></b><br> | ||
− | A toxin-antitoxin system is a system composed of two gene products, of which one specifies a cell toxin and the other an antitoxin, which | + | A toxin-antitoxin system is a system composed of two gene products, of which one specifies a cell toxin and the other an antitoxin, which neutralises the toxic effect caused by the toxin. In <i>E. coli</i> K-12 the cytotoxin RelE and antitoxin RelB comprise such a system <span class="reference"><span class="referencetext"><a target="blank" href=" https://www.ncbi.nlm.nih.gov/pubmed/9767574">Gotfredsen M, Gerdes K. The Escherichia coli relBE genes belong to a new toxin-antitoxin gene family. Molecular microbiology. 1998;29(4):1065-76.</a></span></span>. Expression of the cytotoxin RelE inhibits translation in the cells, due to its ability to cleave mRNA found in the A-site of the ribosome <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/12526800">Pedersen K, Zavialov AV, Pavlov MY, Elf J, Gerdes K, Ehrenberg M. The bacterial toxin RelE displays codon-specific cleavage of mRNAs in the ribosomal A site. Cell. 2003;112(1):131-40.</a></span></span>. RelB neutralise the toxic effect of RelE through interaction between the two proteins. In situations of amino acid starvation, it is appropriate for the bacteria to halt the translation in order to avoid errors owing to absent amino acids. Consequently, one of the exciting factors for the expression of RelE is conditioned by amino acid starvation <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/12526800">Pedersen K, Zavialov AV, Pavlov MY, Elf J, Gerdes K, Ehrenberg M. The bacterial toxin RelE displays codon-specific cleavage of mRNAs in the ribosomal A site. Cell. 2003;112(1):131-40.</a></span></span>. |
<br> | <br> | ||
Whether the cell lie dormant in response to expression of RelE depends on the ratio of RelB and RelE present in the cell. Several studies have shown that RelB RelE form a complex with RelB:RelE stoichiometry of 2:1 <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/19747491">Overgaard M, Borch J, Gerdes K. RelB and RelE of Escherichia coli form a tight complex that represses transcription via the ribbon-helix-helix motif in RelB. Journal of molecular biology. 2009;394(2):183-96.</a></span></span><span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/18532983">Overgaard M, Borch J, Jorgensen MG, Gerdes K. Messenger RNA interferase RelE controls relBE transcription by conditional cooperativity. Molecular microbiology. 2008;69(4):841-57.</a></span></span>, When the RelB:RelE stoichiometric-ratio is lowered to 1:1, studies show that RelB is not able to protect the cells against the RelE-caused translational inhibition <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/18532983">Overgaard M, Borch J, Jorgensen MG, Gerdes K. Messenger RNA interferase RelE controls relBE transcription by conditional cooperativity. Molecular microbiology. 2008;69(4):841-57.</a></span></span>. To prevent free RelE circulating and discharging toxic effects in the cells under favorable conditions, studies in vivo have shown that RelB is present in 10x higher concentrations than RelE <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/19747491">Overgaard M, Borch J, Gerdes K. RelB and RelE of Escherichia coli form a tight complex that represses transcription via the ribbon-helix-helix motif in RelB. Journal of molecular biology. 2009;394(2):183-96.</a></span></span>. The heterologous induction of RelE could cause dissonance in the RelB:RelE ratio leading to serious consequences for the cells <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/11717402">Christensen SK, Mikkelsen M, Pedersen K, Gerdes K. RelE, a global inhibitor of translation, is activated during nutritional stress. Proceedings of the National Academy of Sciences of the United States of America. 2001;98(25):14328-33.</a></span></span>. The bacteria are not killed when RelE is present in abundance, but high expression of the RelE gene makes awakening of the bacterial cells a challenge <span class="reference"><span class="referencetext"><a target="blank" href=" https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3294780/">Tashiro Y, Kawata K, Taniuchi A, Kakinuma K, May T, Okabe S. RelE-Mediated Dormancy Is Enhanced at High Cell Density in Escherichia coli. J Bacteriol. 2012;194(5):1169-76.</a></span></span>. Hence, introducing a toxin to cells in a successful manner constitutes a challenge. | Whether the cell lie dormant in response to expression of RelE depends on the ratio of RelB and RelE present in the cell. Several studies have shown that RelB RelE form a complex with RelB:RelE stoichiometry of 2:1 <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/19747491">Overgaard M, Borch J, Gerdes K. RelB and RelE of Escherichia coli form a tight complex that represses transcription via the ribbon-helix-helix motif in RelB. Journal of molecular biology. 2009;394(2):183-96.</a></span></span><span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/18532983">Overgaard M, Borch J, Jorgensen MG, Gerdes K. Messenger RNA interferase RelE controls relBE transcription by conditional cooperativity. Molecular microbiology. 2008;69(4):841-57.</a></span></span>, When the RelB:RelE stoichiometric-ratio is lowered to 1:1, studies show that RelB is not able to protect the cells against the RelE-caused translational inhibition <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/18532983">Overgaard M, Borch J, Jorgensen MG, Gerdes K. Messenger RNA interferase RelE controls relBE transcription by conditional cooperativity. Molecular microbiology. 2008;69(4):841-57.</a></span></span>. To prevent free RelE circulating and discharging toxic effects in the cells under favorable conditions, studies in vivo have shown that RelB is present in 10x higher concentrations than RelE <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/19747491">Overgaard M, Borch J, Gerdes K. RelB and RelE of Escherichia coli form a tight complex that represses transcription via the ribbon-helix-helix motif in RelB. Journal of molecular biology. 2009;394(2):183-96.</a></span></span>. The heterologous induction of RelE could cause dissonance in the RelB:RelE ratio leading to serious consequences for the cells <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/11717402">Christensen SK, Mikkelsen M, Pedersen K, Gerdes K. RelE, a global inhibitor of translation, is activated during nutritional stress. Proceedings of the National Academy of Sciences of the United States of America. 2001;98(25):14328-33.</a></span></span>. The bacteria are not killed when RelE is present in abundance, but high expression of the RelE gene makes awakening of the bacterial cells a challenge <span class="reference"><span class="referencetext"><a target="blank" href=" https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3294780/">Tashiro Y, Kawata K, Taniuchi A, Kakinuma K, May T, Okabe S. RelE-Mediated Dormancy Is Enhanced at High Cell Density in Escherichia coli. J Bacteriol. 2012;194(5):1169-76.</a></span></span>. Hence, introducing a toxin to cells in a successful manner constitutes a challenge. | ||
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<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/f/f6/T--SDU-Denmark--model-kort-graph.svg" type="image/svg+xml" style="width:100%;"></object></div> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/f/f6/T--SDU-Denmark--model-kort-graph.svg" type="image/svg+xml" style="width:100%;"></object></div> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 2.</b> Left: The time required for the bacteria to enter dormancy varies with the expression level of RelB. |
Right: Only one of the tested configurations, RelB<sub>2</sub>:50-RelE:35, causes the bacteria to regain their activity within the modelled time. The data is based on the simulation of 1000 independent bacteria.</p></div><br class="noContent"> | Right: Only one of the tested configurations, RelB<sub>2</sub>:50-RelE:35, causes the bacteria to regain their activity within the modelled time. The data is based on the simulation of 1000 independent bacteria.</p></div><br class="noContent"> | ||
<p> | <p> | ||
− | The simulated data revealed, that when enhanced RelE production is implemented in order to induce dormancy in <i>E. coli</i>, the effect come easily. However, <span class="highlighted"> implementation of RelB expression is also found necessary</span> to ensure that the bacteria are able to enter an active state again. <br> | + | The simulated data revealed, that when enhanced RelE production is implemented, in order to induce dormancy in <i>E. coli</i>, the effect come easily. However, <span class="highlighted"> implementation of RelB expression is also found necessary</span> to ensure that the bacteria are able to enter an active state again. <br> |
− | The model showed that <span class="highlighted">the system is sensitive to the RelE:RelB ratio</span> as well as the total amount of produced toxin. As seen in | + | The model showed that <span class="highlighted">the system is sensitive to the RelE:RelB ratio</span>, as well as the total amount of produced toxin. As seen in Figure 2, implementation with production rates in the vicinity of <span class="highlighted">50 and 35 molecules per minute for RelB and RelE respectively, was found to be suitable for balancing our system</span>; the bacteria lay dormant within the computed time and re-enter an active state within minutes. <br> |
− | The simulated data made it evident | + | The simulated data made it evident that <span class="highlighted">implementing an optimised dormancy system comprises a challenge</span>, as the individual expression levels of RelE and RelB, as well as their interaction, has a crucial impact on the regulation of dormancy. Thus, controlled gene expression of both RelE and RelB is required to implement a controllable dormancy system in the PowerLeaf. |
+ | <br> | ||
+ | If you want to dig deeper into this crucial modelling of the dormancy system, read the full results <span class="btn-link btn-lg" data-toggle="modal" data-target="#model-results">here</span>. </p> | ||
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<p> | <p> | ||
− | Modelling of the effects of different RelE and RelB expression levels were performed as an important aspect in the implementation of the RelE-RelB toxin-antitoxin system. The toxin RelE constrains bacterial growth by mRNA degradation, thereby inhibiting translation, whereas the antitoxin RelB inhibits this toxic effect by forming complexes with RelE. As seen in | + | Modelling of the effects of different RelE and RelB expression levels were performed as an important aspect in the implementation of the RelE-RelB toxin-antitoxin system. The toxin RelE constrains bacterial growth by mRNA degradation, thereby inhibiting translation, whereas the antitoxin RelB inhibits this toxic effect by forming complexes with RelE. As seen in Figure 1, three different protein complexes are formed, namely RelB<sub>2</sub>, RelB<sub>2</sub>RelE, and RelB<sub>2</sub>RelE<sub>2</sub>, containing zero, one, and two RelE molecules respectively <span class="reference"><span class="referencetext"><a target="blank" href="https://doi.org/10.1016/j.jmb.2008.04.039.">Guang-Yao Li, Yonglong Zhang, Masayori Inouye, Mitsuhiko Ikura, Structural Mechanism of Transcriptional Autorepression of the Escherichia coli RelB/RelE Antitoxin/Toxin Module, In Journal of Molecular Biology, Volume 380, Issue 1, 2008, Pages 107-119, ISSN 0022-2836</a></span></span>. |
</p><br> | </p><br> | ||
<object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/9/91/T--SDU-Denmark--modelling-figure-1-rele-relb.svg" type="image/svg+xml" style="width:100%;"></object> | <object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/9/91/T--SDU-Denmark--modelling-figure-1-rele-relb.svg" type="image/svg+xml" style="width:100%;"></object> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 1.</b> The three toxin-antitoxin complexes RelB<sub>2</sub>, RelB<sub>2</sub>RelE, and RelB<sub>2</sub>RelE<sub>2</sub>.</p></div><br class="noContent"> |
− | <p>The expression of both RelE and RelB is regulated by the <i>relBE</i> promoter, which is influenced differently by each of the complexes, as seen in | + | <p>The expression of both RelE and RelB is regulated by the <i>relBE</i> promoter, which is influenced differently by each of the complexes, as seen in Figure 2. When small amounts of RelE is present, RelB<sub>2</sub> and RelB<sub>2</sub>RelE repress transcription through <i>relBE</i> by binding to the operator sequence. However, when high amounts of RelE are present, the toxin mitigates this repression by reacting with complexes bound to the operator sequence <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3413109/">Cataudella I., Trusina A., Sneppen K., Gerdes K., Mitarai N. Conditional cooperativity in toxin-antitoxin regulation prevents random toxin activation and promotes fast translational recovery. Nucleic Acids Res. 2012;40:6424–6434. doi: 10.1093/nar/gks297</a></span></span>. |
</p> | </p> | ||
<object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/6/61/T--SDU-Denmark--modelling-figure-2-rele-relb.svg" type="image/svg+xml" style="width:100%;"></object> | <object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/6/61/T--SDU-Denmark--modelling-figure-2-rele-relb.svg" type="image/svg+xml" style="width:100%;"></object> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 2.</b> The interactions between the toxin-antitoxin complexes and the relBE promoter controlling the expression of RelE and RelB. RelE mediates the degradation of mRNA, thereby inhibiting translation.</p></div><br class="noContent"> |
<p>During starvation, the half-life of RelB decreases significantly due to a Lon-protease<span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/18532983">Overgaard, M., Borch, J., Jørgensen, M. G. and Gerdes, K. (2008), Messenger RNA interferase RelE controls relBE transcription by conditional cooperativity. Molecular Microbiology, 69: 841–857. doi:10.1111/j.1365-2958.2008.06313.x</a></span></span>, causing a shift in the equilibrium of RelB and RelE to a higher level of RelE. In a non-starvation situation, the interactions with the operator sequence keeps the amount of free RelE at a low level, thereby stabilising the system <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3413109/">Cataudella I., Trusina A., Sneppen K., Gerdes K., Mitarai N. Conditional cooperativity in toxin-antitoxin regulation prevents random toxin activation and promotes fast translational recovery. Nucleic Acids Res. 2012;40:6424–6434. doi: 10.1093/nar/gks297</a></span></span>. In our simulation, the shift in equilibrium is made by introducing additional expression of RelE. <br> | <p>During starvation, the half-life of RelB decreases significantly due to a Lon-protease<span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/18532983">Overgaard, M., Borch, J., Jørgensen, M. G. and Gerdes, K. (2008), Messenger RNA interferase RelE controls relBE transcription by conditional cooperativity. Molecular Microbiology, 69: 841–857. doi:10.1111/j.1365-2958.2008.06313.x</a></span></span>, causing a shift in the equilibrium of RelB and RelE to a higher level of RelE. In a non-starvation situation, the interactions with the operator sequence keeps the amount of free RelE at a low level, thereby stabilising the system <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3413109/">Cataudella I., Trusina A., Sneppen K., Gerdes K., Mitarai N. Conditional cooperativity in toxin-antitoxin regulation prevents random toxin activation and promotes fast translational recovery. Nucleic Acids Res. 2012;40:6424–6434. doi: 10.1093/nar/gks297</a></span></span>. In our simulation, the shift in equilibrium is made by introducing additional expression of RelE. <br> | ||
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<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/6/6a/T--SDU-Denmark--ren-rele.svg" type="image/svg+xml" style="width:100%;"></object></div> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/6/6a/T--SDU-Denmark--ren-rele.svg" type="image/svg+xml" style="width:100%;"></object></div> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 1.</b> The increase of free RelE molecules in <i>E. coli</i> cells, after activation of the artificial RelE production, shown logarithmically. The condition for induced dormancy is an amount of free RelE molecules around tens of copies. The three highest levels of RelE production, correlating with the highest promoter strengths, show little difference in the time at which dormancy occurs. When the RelE production is set to 10.5 molecules per minute, dormancy is induced more slowly and stabilises at lower concentrations. The lowest RelE production value does not trigger dormancy, and has only little effect on the system.</p></div><br class="noContent"> |
<p><b>RelB is Required for Activation of Bacteria after Dormant State</b><br class="miniBreak"> | <p><b>RelB is Required for Activation of Bacteria after Dormant State</b><br class="miniBreak"> | ||
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<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/6/6a/T--SDU-Denmark--Wakeup.svg" type="image/svg+xml" style="width:100%;"></object></div> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/6/6a/T--SDU-Denmark--Wakeup.svg" type="image/svg+xml" style="width:100%;"></object></div> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 2.</b> The logarithmic plots shows that the decrease in free RelE in dormant bacteria is low without artificial expression of RelB. None of the simulated bacteria reentered an active state within the modelled time.</p></div><br class="noContent"> |
<p><b>Appropriate Ratio of RelE and RelB Expression is Essential</b><br class="miniBreak"> | <p><b>Appropriate Ratio of RelE and RelB Expression is Essential</b><br class="miniBreak"> | ||
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<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/3/37/T--SDU-Denmark--Dormancy-variations.svg" type="image/svg+xml" style="width:100%;"></object></div> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/3/37/T--SDU-Denmark--Dormancy-variations.svg" type="image/svg+xml" style="width:100%;"></object></div> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 3.</b> The variation in time required for the bacteria to enter an active state for different expression levels of RelB is dependent on the level of RelE expression. All configurations achieve dormancy within the modelled time.</p></div><br class="noContent"> |
<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/3/33/T--SDU-Denmark--Reactivation.svg" type="image/svg+xml" style="width:100%;"></object></div> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/3/33/T--SDU-Denmark--Reactivation.svg" type="image/svg+xml" style="width:100%;"></object></div> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 4.</b> RelB<sub>2</sub>:50-RelE:35 induces an active state within minutes, whereas RelB:35-RelE:35 only causes few of the bacteria to enter an active state. In the remaining configurations all bacteria remained dormant.</p></div><br class="noContent"> |
<br class="noContent"> | <br class="noContent"> | ||
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<p class="P-Larger"><b>Approach</b></p><br> | <p class="P-Larger"><b>Approach</b></p><br> | ||
<p> | <p> | ||
− | In 2004 the <a href="https://2004.igem.org/austin.cgi" target="_blank">Austen and UCSF iGEM team</a> created a <span class="highlighted">device sensitive to light,</span> laying the foundation for the <a href="http://parts.igem.org/Coliroid" target="_blank">Coliroid project</a>. In this project, the <span class="highlighted">system is combined with the RelE-RelB toxin-antitoxin system</span> in the endeavour to mediate <span class="highlighted">light-dependent dormancy in bacteria</span>. As tight regulation is required for the RelE-RelB system <span class="reference"><span class="referencetext"><a target="blank" href=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3294780/">Tashiro Y, Kawata K, Taniuchi A, Kakinuma K, May T, Okabe S. RelE-Mediated Dormancy Is Enhanced at High Cell Density in Escherichia coli. J Bacteriol. 2012;194(5):1169-76.</a></span></span>, <span class="highlighted">modelling of the toxin-antitoxin system</span>is essential. The impact of different RelE-RelB expression levels was simulated by modelling. Using the results obtained by modelling, a hypothetical working system-design was devised. | + | In 2004 the <a href="https://2004.igem.org/austin.cgi" target="_blank">Austen and UCSF iGEM team</a> created a <span class="highlighted">device sensitive to light,</span> laying the foundation for the <a href="http://parts.igem.org/Coliroid" target="_blank">Coliroid project</a>. In this project, the <span class="highlighted">system is combined with the RelE-RelB toxin-antitoxin system</span> in the endeavour to mediate <span class="highlighted">light-dependent dormancy in bacteria</span>. As tight regulation is required for the RelE-RelB system <span class="reference"><span class="referencetext"><a target="blank" href=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3294780/">Tashiro Y, Kawata K, Taniuchi A, Kakinuma K, May T, Okabe S. RelE-Mediated Dormancy Is Enhanced at High Cell Density in Escherichia coli. J Bacteriol. 2012;194(5):1169-76.</a></span></span>, <span class="highlighted">modelling of the toxin-antitoxin system</span> is essential. The impact of different RelE-RelB expression levels was simulated by modelling. Using the results obtained by this modelling, a hypothetical working system-design was devised. |
<br> | <br> | ||
− | On basis of the modulated system, the potential of different vectors and promoters in various combinations was tested. This constitutes the foundation for how the design of the light | + | On basis of the modulated system, the potential of different vectors and promoters in various combinations was tested. This constitutes the foundation for how the design of the light-dependent dormancy system in <i>E. coli</i> has been optimised, and the final approach shaped. Ultimately, the light-dependent dormancy system, which is illustrated in Figure 3, was composed of the following parts: |
</p> | </p> | ||
<ul class="list"> | <ul class="list"> | ||
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<br class="noContent"> | <br class="noContent"> | ||
<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/7/73/T--SDU-Denmark--final-approach-light-sensing-system.svg" type="image/svg+xml" style="width:100%;"></object></div><br> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/7/73/T--SDU-Denmark--final-approach-light-sensing-system.svg" type="image/svg+xml" style="width:100%;"></object></div><br> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 3.</b> The final design of the light-dependent dormancy system. RelE under control of the OmpR-regulated promoter on the chromosome or a low copy vector, RelB under the control of the pBAD promoter on a low copy vector, and the photocontrol device controlled by the PenI-regulated promoter on a high copy vector.</p></div><br class="noContent"> |
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<p><b>Balancing Bacterial Dormancy Requires Accurate Regulation of the System</b><br> | <p><b>Balancing Bacterial Dormancy Requires Accurate Regulation of the System</b><br> | ||
− | The genes needed for inducing dormancy when the bacteria are not exposed to light, are found in the photocontrol device part, <a href="http://parts.igem.org/Part:BBa_K519030" target="_blank">BBa_K519030</a>. This part is composed of three genes named <i>ho1</i>, <i>pcyA</i>, and <i>cph8</i>, all of which are essential to ensure the cells ability to respond to red light. When the photocontrol device is exposed to light, a phosphorylation cascade activates the transcription factor OmpR, which in turn induces transcription through the OmpR-regulated promoter, <a href="http://parts.igem.org/Part:BBa_R0082" target="_blank">BBa_R0082</a>. This system is combined with the RelE-RelB toxin-antitoxin system in the endeavour to mediate light-dependent dormancy in bacteria. In the first considered design of the light-dependent dormancy system, the aim was to clone the photocontrol device, <a href="http://parts.igem.org/Part:BBa_K519030" target="_blank">BBa_K519030</a>, under control of a constitutive promoter, RelE under control of the OmpR-regulated promoter, <a href="http://parts.igem.org/Part:BBa_R0082" target="_blank">BBa_R0082</a>, and RelB under control of a constitutive promoter, all into one high copy BioBrick assembly plasmid pSB1C3, as seen on | + | The genes needed for inducing dormancy when the bacteria are not exposed to light, are found in the photocontrol device part, <a href="http://parts.igem.org/Part:BBa_K519030" target="_blank">BBa_K519030</a>. This part is composed of three genes named <i>ho1</i>, <i>pcyA</i>, and <i>cph8</i>, all of which are essential to ensure the cells ability to respond to red light. When the photocontrol device is exposed to light, a phosphorylation cascade activates the transcription factor OmpR, which in turn induces transcription through the OmpR-regulated promoter, <a href="http://parts.igem.org/Part:BBa_R0082" target="_blank">BBa_R0082</a>. This system is combined with the RelE-RelB toxin-antitoxin system in the endeavour to mediate light-dependent dormancy in bacteria. In the first considered design of the light-dependent dormancy system, the aim was to clone the photocontrol device, <a href="http://parts.igem.org/Part:BBa_K519030" target="_blank">BBa_K519030</a>, under control of a constitutive promoter, RelE under control of the OmpR-regulated promoter, <a href="http://parts.igem.org/Part:BBa_R0082" target="_blank">BBa_R0082</a>, and RelB under control of a constitutive promoter, all into one high copy BioBrick assembly plasmid pSB1C3, as seen on Figure 1.</p> |
<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/e/e3/T--SDU-Denmark--light-sensing-plasmid-figure-1.svg" type="image/svg+xml" style="width:100%;"></object></div> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/e/e3/T--SDU-Denmark--light-sensing-plasmid-figure-1.svg" type="image/svg+xml" style="width:100%;"></object></div> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 1.</b> All three components of the light-dependent dormancy system cloned into one high copy plasmid.</p></div><br class="noContent"> |
<br class="noContent"> | <br class="noContent"> | ||
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<p> | <p> | ||
<b>The Photocontrol Device was Placed under Control of a Constitutive Promoter</b><br> | <b>The Photocontrol Device was Placed under Control of a Constitutive Promoter</b><br> | ||
− | From the <a href="http://parts.igem.org/Promoters/Catalog/Anderson" target="_blank">constitutive promoter family</a> the weak promoter, <a href="http://parts.igem.org/Part:BBa_J23114" target="_blank">BBa_J23114</a>, the two medium promoters, <a href="http://parts.igem.org/Part:BBa_J23106" target="_blank">BBa_J23106</a>, and <a href="http://parts.igem.org/Part:BBa_J23110" target="_blank">BBa_J23110</a>, and the strong promoter, <a href="http://parts.igem.org/Part:BBa_J23102" target="_blank">BBa_J23102</a>, were tested by fluorescence microscopy to determine which one to use for expression of the photocontrol device and RelB. Overnight cultures of the submitted parts expressed in <i>E. coli</i> TOP10 illustrated a clear gradient of increasing red fluorescent protein (RFP) expression correlated with the strength of the promoter, as seen on | + | From the <a href="http://parts.igem.org/Promoters/Catalog/Anderson" target="_blank">constitutive promoter family</a> the weak promoter, <a href="http://parts.igem.org/Part:BBa_J23114" target="_blank">BBa_J23114</a>, the two medium promoters, <a href="http://parts.igem.org/Part:BBa_J23106" target="_blank">BBa_J23106</a>, and <a href="http://parts.igem.org/Part:BBa_J23110" target="_blank">BBa_J23110</a>, and the strong promoter, <a href="http://parts.igem.org/Part:BBa_J23102" target="_blank">BBa_J23102</a>, were tested by fluorescence microscopy to determine which one to use for expression of the photocontrol device and RelB. Overnight cultures of the submitted parts expressed in <i>E. coli</i> TOP10 illustrated a clear gradient of increasing red fluorescent protein (RFP) expression correlated with the strength of the promoter, as seen on Figure 2.</p><br> |
<div style="text-align:center;"> | <div style="text-align:center;"> | ||
<img class="highlighted-image" src="https://static.igem.org/mediawiki/2017/9/97/T--SDU-Denmark--color-gradient-constitutive-promoter.jpg" width="100%"/> | <img class="highlighted-image" src="https://static.igem.org/mediawiki/2017/9/97/T--SDU-Denmark--color-gradient-constitutive-promoter.jpg" width="100%"/> | ||
</div> | </div> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 2.</b> Cultures of <i>E. coli</i> TOP10. From left to right: WT, the weak promoter, <a href="http://parts.igem.org/Part:BBa_J23114" target="_blank">BBa_J23114</a>, the two medium promoters, <a href="http://parts.igem.org/Part:BBa_J23110" target="_blank">BBa_J23110</a>, and <a href="http://parts.igem.org/Part:BBa_J23106" target="_blank">BBa_J23106</a>, and the strong promoter, <a href="http://parts.igem.org/Part:BBa_J23102" target="_blank">BBa_J23102</a>.</p></div><br class="noContent"> |
<p> | <p> | ||
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<b>Regulation of the OmpR-dependent Promoter Required a Low Copy Vector </b><br> | <b>Regulation of the OmpR-dependent Promoter Required a Low Copy Vector </b><br> | ||
− | The first construct containing the genes required for the light-induced dormancy was designed as shown in | + | The first construct containing the genes required for the light-induced dormancy was designed as shown in Figure 1. As the conducted modelling clarified, the necessity for stringent regulation of the RelE and RelB expression, the properties of the OmpR-regulated promoter were studied thoroughly. To assess the functionality of the OmpR-regulated promoter in practice, a reporter system containing the OmpR-regulated promoter controlling RFP was cloned into the <i>E. coli</i> strain MG1655 ΔOmpR. The phenotype of the resulting cultures revealed a dysregulation of the OmpR-regulated promoter. Thorough research lead to the finding that the OmpR-dependent promoter is not controllable when cloned on a high copy vector. As the modelling revealed, and which is evident from <span class="reference-2">Figure 2-Main-Page<span class="referencetext-2"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/f/f6/T--SDU-Denmark--model-kort-graph.svg" type="image/svg+xml" style="width:100%;"></object></span></span>, a relatively low expression of RelE is required to induce dormancy, whereas high expression levels quickly result in overshooting. Since the OmpR-regulated promoter is an integrated part of the light sensing system, replacement is not an option. Therefore, the variability of the <i>relE</i> gene copy number was studied, and it was found that the OmpR-regulated promoter should be cloned into the bacterial chromosome or a low copy vector to obtain proper regulation <span class="reference"><span class="referencetext"><a target="blank" href=”https://www.ncbi.nlm.nih.gov/pubmed/16306980">Levskaya A, Chevalier AA, Tabor JJ, Simpson ZB, Lavery LA, Levy M, et al. Synthetic biology: engineering Escherichia coli to see light. Nature. 2005;438(7067):441-2.</a></span></span>. This intriguing finding let to the aspiration to investigate the controllability of the OmpR-dependent promoter on vectors with different copy numbers compared to the chromosome, thereby improving the characterisation of the promoter for the benefit to future iGEM teams. |
<br> | <br> | ||
− | To incorporate DNA onto the bacterial chromosome, homologous recombination with the red λ recombinase is a suitable approach <span class="reference"><span class="referencetext"><a target="blank" href=”https://www.ncbi.nlm.nih.gov/pubmed/2958633">Thompson JF, de Vargas LM, Skinner SE, Landy A. Protein-protein interactions in a higher-order structure direct lambda site-specific recombination. Journal of molecular biology. 1987;195(3):481-93.</a></span></span>. Using this technique, a short fragment of chromosomal DNA at the bacterial attachment site attB <span class="reference"><span class="referencetext"><a target="blank" href=”https://www.ncbi.nlm.nih.gov/pubmed/14687564">Groth AC, Calos MP. Phage integrases: biology and applications. Journal of molecular biology. 2004;335(3):667-78.</a></span></span> can be replaced with a linear DNA fragment encoding the OmpR-dependent promoter, RelE, and an chloramphenicol resistance cassette. Using polymerase chain reaction (PCR), the linear DNA sequence was flanked by sequences, which are homologous to part of the chromosome. The linear DNA fragment was electroporated into bacteria containing the pKD46 plasmid, encoding the red λ recombinase <span class="reference"><span class="referencetext"><a target="blank" href=”https://www.ncbi.nlm.nih.gov/pubmed/2958633">Thompson JF, de Vargas LM, Skinner SE, Landy A. Protein-protein interactions in a higher-order structure direct lambda site-specific recombination. Journal of molecular biology. 1987;195(3):481-93.</a></span></span>, which mediated the recombination. The fundamental concept of this approach is illustrated in | + | To incorporate DNA onto the bacterial chromosome, homologous recombination with the red λ recombinase is a suitable approach <span class="reference"><span class="referencetext"><a target="blank" href=”https://www.ncbi.nlm.nih.gov/pubmed/2958633">Thompson JF, de Vargas LM, Skinner SE, Landy A. Protein-protein interactions in a higher-order structure direct lambda site-specific recombination. Journal of molecular biology. 1987;195(3):481-93.</a></span></span>. Using this technique, a short fragment of chromosomal DNA at the bacterial attachment site attB <span class="reference"><span class="referencetext"><a target="blank" href=”https://www.ncbi.nlm.nih.gov/pubmed/14687564">Groth AC, Calos MP. Phage integrases: biology and applications. Journal of molecular biology. 2004;335(3):667-78.</a></span></span> can be replaced with a linear DNA fragment encoding the OmpR-dependent promoter, RelE, and an chloramphenicol resistance cassette. Using polymerase chain reaction (PCR), the linear DNA sequence was flanked by sequences, which are homologous to part of the chromosome. The linear DNA fragment was electroporated into bacteria containing the pKD46 plasmid, encoding the red λ recombinase <span class="reference"><span class="referencetext"><a target="blank" href=”https://www.ncbi.nlm.nih.gov/pubmed/2958633">Thompson JF, de Vargas LM, Skinner SE, Landy A. Protein-protein interactions in a higher-order structure direct lambda site-specific recombination. Journal of molecular biology. 1987;195(3):481-93.</a></span></span>, which mediated the recombination. The fundamental concept of this approach is illustrated in Figure 3. |
<br></p> | <br></p> | ||
<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/2/2a/T--SDU-Denmark--homolog-recombination-figure.svg" type="image/svg+xml" style="width:100%;"></object></div> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/2/2a/T--SDU-Denmark--homolog-recombination-figure.svg" type="image/svg+xml" style="width:100%;"></object></div> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 3.</b> The principle behind the recombination. By PCR, the two flanking sequences are assembled with the fragment containing the chloramphenicol resistance gene (camR), the OmpR-regulated promoter, and the relE gene. The flanking sequences are homologous to part of the chromosome around the bacterial attachment site (attB), enabling the homologous recombination.</p></div><br class="noContent"> |
<p> | <p> | ||
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<b>The Final Approach for the Three Components Comprised Three Different Vectors</b><br> | <b>The Final Approach for the Three Components Comprised Three Different Vectors</b><br> | ||
− | Based on the modelling the system approaches reviewed in the preceding part, the final design, which is illustrated on | + | Based on the modelling the system approaches reviewed in the preceding part, the final design, which is illustrated on Figure 4, was established. Ultimately, the dormancy system was composed of the photocontrol device controlled by the PenI-regulated promoter on a high copy vector, RelB controlled by pBAD, <a href="http://parts.igem.org/wiki/index.php?title=Part:BBa_K2449031" target="_blank">BBa_K2449031</a>, on a low copy vector and RelE controlled by the OmpR-regulated promoter on either a low copy vector or the chromosome. |
<br> | <br> | ||
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<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/7/73/T--SDU-Denmark--final-approach-light-sensing-system.svg" type="image/svg+xml" style="width:100%;"></object></div> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/7/73/T--SDU-Denmark--final-approach-light-sensing-system.svg" type="image/svg+xml" style="width:100%;"></object></div> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 4.</b> The final design of the light-dependent dormancy system. RelE under control of the OmpR-regulated promoter on the chromosome or a low copy vector, RelB under the control of the pBAD promoter on a low copy vector, and the photocontrol device controlled by the PenI-regulated promoter on a high copy plasmid.</p></div><br class="noContent"> |
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+ | <div style="text-align:center;"><p style="font-size:14px;"><i><a href="#project-results-dormancy-system">Click here if you wish to go directly to the Project Demonstration & Results section of the Dormancy System.</a></i></p></div><br> | ||
− | <div style="text-align:center;"><p style="font-size:14px;"><i><a href="#project-design">Click here to return to the | + | <div style="text-align:center;"><p style="font-size:14px;"><i><a href="#project-design">Click here to return to the Project Design overview.</a></i></p></div> |
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− | <p class="P-Larger"><b> | + | <p class="P-Larger"><b>Introduction</b></p><br> |
<p> | <p> | ||
Carbon fixation in autotrophic organisms is responsible for the net fixation of 7×10<sup>16</sup> g carbon annually <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/?term=Berg+(2011)+Ecological+Aspects+of+the+Distribution+of+Different+Autotrophic+CO2+Fixation+Pathways">Berg IA. Ecological aspects of the distribution of different autotrophic CO2 fixation pathways. Applied and Environmental Microbiology. 2011;77(6):1925-36.</a></span></span>. Six different pathways related to carbon fixation have been discovered, but the most widespread of these, is the Calvin-Benson-Bassham (CBB) cycle found in photosynthetic eukaryotes, e.g. plants and algae, as well as in photo- and chemosynthetic bacteria <span class="reference"><span class="referencetext"><a target="blank" href="https://books.google.dk/books?id=puEsBAAAQBAJ&pg=PA21&lpg=PA21&dq=calvin+cycle+most+widespread&source=bl&ots=8QGIRwvzDj&sig=7jfO_H3MSc67XxB8xRM3nVdavdA&hl=en&sa=X&ved=0ahUKEwj64OL0-pXVAhXrbZoKHbEWCzcQ6AEINjAD#v=onepage&q=cyano&f=false">B. Bowien MG, R. Klintworth, U. Windhövel. Metabolic and Molecular Regulation of the CO2-assimilating Enzyme System in Aerobic Chemoautotrophs. Microbial Growth on C1 Compounds: Proceedings of the 5th International Symposion. 1st ed. Institute for Microbiology, Georg-August-University Göttingen, Federal Republic of Germany: Martinus Nijhoff Publishers; 1987.</a></span></span>. <span class="highlighted">Out of the eleven enzymes needed for the Calvin cycle, only three are heterologous to <i>E. coli</i></span>, namely; ribulose-1,5-bisphosphate carboxylase/oxygenase (<span class="highlighted">RuBisCo</span>), sedoheptulose-1,7-bisphosphatase (<span class="highlighted">SBPase</span>) and phosphoribulokinase (<span class="highlighted">PRK</span>). By the concurrent heterologous expression of the three genes encoding these enzymes, <i>E. coli</i> can be engineered to perform the full Calvin cycle.</p> | Carbon fixation in autotrophic organisms is responsible for the net fixation of 7×10<sup>16</sup> g carbon annually <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/?term=Berg+(2011)+Ecological+Aspects+of+the+Distribution+of+Different+Autotrophic+CO2+Fixation+Pathways">Berg IA. Ecological aspects of the distribution of different autotrophic CO2 fixation pathways. Applied and Environmental Microbiology. 2011;77(6):1925-36.</a></span></span>. Six different pathways related to carbon fixation have been discovered, but the most widespread of these, is the Calvin-Benson-Bassham (CBB) cycle found in photosynthetic eukaryotes, e.g. plants and algae, as well as in photo- and chemosynthetic bacteria <span class="reference"><span class="referencetext"><a target="blank" href="https://books.google.dk/books?id=puEsBAAAQBAJ&pg=PA21&lpg=PA21&dq=calvin+cycle+most+widespread&source=bl&ots=8QGIRwvzDj&sig=7jfO_H3MSc67XxB8xRM3nVdavdA&hl=en&sa=X&ved=0ahUKEwj64OL0-pXVAhXrbZoKHbEWCzcQ6AEINjAD#v=onepage&q=cyano&f=false">B. Bowien MG, R. Klintworth, U. Windhövel. Metabolic and Molecular Regulation of the CO2-assimilating Enzyme System in Aerobic Chemoautotrophs. Microbial Growth on C1 Compounds: Proceedings of the 5th International Symposion. 1st ed. Institute for Microbiology, Georg-August-University Göttingen, Federal Republic of Germany: Martinus Nijhoff Publishers; 1987.</a></span></span>. <span class="highlighted">Out of the eleven enzymes needed for the Calvin cycle, only three are heterologous to <i>E. coli</i></span>, namely; ribulose-1,5-bisphosphate carboxylase/oxygenase (<span class="highlighted">RuBisCo</span>), sedoheptulose-1,7-bisphosphatase (<span class="highlighted">SBPase</span>) and phosphoribulokinase (<span class="highlighted">PRK</span>). By the concurrent heterologous expression of the three genes encoding these enzymes, <i>E. coli</i> can be engineered to perform the full Calvin cycle.</p> | ||
<br> | <br> | ||
<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/c/c2/T--SDU-Denmark--calvin-cycle.svg" type="image/svg+xml" style="width:75%;"></object></div> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/c/c2/T--SDU-Denmark--calvin-cycle.svg" type="image/svg+xml" style="width:75%;"></object></div> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 4.</b> A simplified illustration of the Calvin cycle, with the enzymes heterologous to <i>E. coli</i> and their respective substrates and products shown.</p></div><br class="noContent"> |
<p>The <span class="highlighted">carboxysome is a microcompartment</span> utilised by many chemoautotrophic bacteria, including cyanobacteria, as a CO<sub>2</sub> accumulating mechanism to <span class="highlighted">increase carbon fixation efficiency </span>. This organelle-like polyhedral body is able to increase the internal concentrations of inorganic carbon by 4000-fold compared to the external concentration <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4027813/">Mangan NM, Brenner MP. Systems analysis of the CO(2) concentrating mechanism in cyanobacteria. eLife. 2014;3.</a></span></span>. One type of carboxysome, is the ɑ-carboxysome, which consists of a proteinaceous outer shell composed of <span class="highlighted">six different shell proteins designated CsoS1ABCD and CsoS4AB. This shell encloses RuBisCo, the shell associated protein (CsoS2), and the enzyme carbonic anhydrase (CsoS3)</span>. In the proteobacteria <i>Halothiobacillus neapolitanus</i>, these genes are clustered into the <span class="highlighted"><i>cso</i> operon</span>. The carbonic anhydrase converts HCO<sub>3</sub><sup>-</sup>, which diffuses passively into the carboxysome, to CO<sub>2</sub>, thereby driving the continued diffusion of HCO<sub>3</sub><sup>-</sup> into the microcompartment <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4027813/">Mangan NM, Brenner MP. Systems analysis of the CO(2) concentrating mechanism in cyanobacteria. eLife. 2014;3.</a></span></span>. The increased CO<sub>2</sub> concentration in the vicinity of RuBisCo increases the rate of carbon fixation by saturating the RuBisCo enzyme and increasing the CO<sub>2</sub> to O<sub>2</sub> ratio, enabling carboxylation to dominate over oxygenation <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4027813/">Mangan NM, Brenner MP. Systems analysis of the CO(2) concentrating mechanism in cyanobacteria. eLife. 2014;3.</a></span></span>. The shell associated protein is essential for the biogenesis of the ɑ-carboxysome <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/25826651">Cai F, Dou Z, Bernstein SL, Leverenz R, Williams EB, Heinhorst S, et al. Advances in Understanding Carboxysome Assembly in Prochlorococcus and Synechococcus Implicate CsoS2 as a Critical Component. Life (Basel, Switzerland). 2015;5(2):1141-71.</a></span></span>.</p><br> | <p>The <span class="highlighted">carboxysome is a microcompartment</span> utilised by many chemoautotrophic bacteria, including cyanobacteria, as a CO<sub>2</sub> accumulating mechanism to <span class="highlighted">increase carbon fixation efficiency </span>. This organelle-like polyhedral body is able to increase the internal concentrations of inorganic carbon by 4000-fold compared to the external concentration <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4027813/">Mangan NM, Brenner MP. Systems analysis of the CO(2) concentrating mechanism in cyanobacteria. eLife. 2014;3.</a></span></span>. One type of carboxysome, is the ɑ-carboxysome, which consists of a proteinaceous outer shell composed of <span class="highlighted">six different shell proteins designated CsoS1ABCD and CsoS4AB. This shell encloses RuBisCo, the shell associated protein (CsoS2), and the enzyme carbonic anhydrase (CsoS3)</span>. In the proteobacteria <i>Halothiobacillus neapolitanus</i>, these genes are clustered into the <span class="highlighted"><i>cso</i> operon</span>. The carbonic anhydrase converts HCO<sub>3</sub><sup>-</sup>, which diffuses passively into the carboxysome, to CO<sub>2</sub>, thereby driving the continued diffusion of HCO<sub>3</sub><sup>-</sup> into the microcompartment <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4027813/">Mangan NM, Brenner MP. Systems analysis of the CO(2) concentrating mechanism in cyanobacteria. eLife. 2014;3.</a></span></span>. The increased CO<sub>2</sub> concentration in the vicinity of RuBisCo increases the rate of carbon fixation by saturating the RuBisCo enzyme and increasing the CO<sub>2</sub> to O<sub>2</sub> ratio, enabling carboxylation to dominate over oxygenation <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4027813/">Mangan NM, Brenner MP. Systems analysis of the CO(2) concentrating mechanism in cyanobacteria. eLife. 2014;3.</a></span></span>. The shell associated protein is essential for the biogenesis of the ɑ-carboxysome <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/25826651">Cai F, Dou Z, Bernstein SL, Leverenz R, Williams EB, Heinhorst S, et al. Advances in Understanding Carboxysome Assembly in Prochlorococcus and Synechococcus Implicate CsoS2 as a Critical Component. Life (Basel, Switzerland). 2015;5(2):1141-71.</a></span></span>.</p><br> | ||
<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/7/73/T--SDU-Denmark--carboxysome.svg" type="image/svg+xml" style="width:70%;"></object></div> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/7/73/T--SDU-Denmark--carboxysome.svg" type="image/svg+xml" style="width:70%;"></object></div> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 5.</b> An illustration of the ɑ-carboxysome. The shell proteins CsoS1ABC and CsoS4AB enclose the enzymes RuBisCo and carbonic anhydrase.</p></div><br class="noContent"> |
− | <p><span class="highlighted">For the Calvin cycle to proceed, energy in the form of ATP and electrons carried by NADPH are required</span>. The photosystems are complexes in photosynthesising organisms that can supply this by photophosphorylation. To engineer <i>E. coli</i> to do photosynthesis, 13 genes is needed for the assembly of chlorophyll a and 17 genes for the assembly of photosystem II, which needs to be heterogeneously expressed. An alternative process, in which a diverse array of phototrophic bacteria and archaea harvest energy from light, is through a retinal-containing protein called proteorhodopsin, which catalyses the light-activated proton efflux across the cell membrane and thereby drive ATP synthesis. Opposed to the photosystems, the proteorhodopsin is anoxygenic and generates no NADPH, which is crucial for the Calvin cycle to proceed <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1892948/">Walter JM, Greenfield D, Bustamante C, Liphardt J. Light-powering Escherichia coli with proteorhodopsin. Proceedings of the National Academy of Sciences of the United States of America. 2007;104(7):2408-12.</a></span></span>. For further information about | + | <p><span class="highlighted">For the Calvin cycle to proceed, energy in the form of ATP and electrons carried by NADPH are required</span>. The photosystems are complexes in photosynthesising organisms that can supply this by photophosphorylation. To engineer <i>E. coli</i> to do photosynthesis, 13 genes is needed for the assembly of chlorophyll a and 17 genes for the assembly of photosystem II, which needs to be heterogeneously expressed. An alternative process, in which a diverse array of phototrophic bacteria and archaea harvest energy from light, is through a retinal-containing protein called proteorhodopsin, which catalyses the light-activated proton efflux across the cell membrane and thereby drive ATP synthesis. Opposed to the photosystems, the proteorhodopsin is anoxygenic and generates no NADPH, which is crucial for the Calvin cycle to proceed <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1892948/">Walter JM, Greenfield D, Bustamante C, Liphardt J. Light-powering Escherichia coli with proteorhodopsin. Proceedings of the National Academy of Sciences of the United States of America. 2007;104(7):2408-12.</a></span></span>. For further information about the carbon fixation, <span class="btn-link btn-lg" data-toggle="modal" data-target="#co2-fixation-theory">read here</span>. |
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<b>Carbon Fixation through the Calvin Cycle</b> | <b>Carbon Fixation through the Calvin Cycle</b> | ||
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− | Carbon fixation in autotrophic organisms is responsible for the net fixation of 7×10<sup>16</sup> g carbon annually, thereby being the most imperative biosynthetic process in nature <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/?term=Berg+(2011)+Ecological+Aspects+of+the+Distribution+of+Different+Autotrophic+CO2+Fixation+Pathways">Berg IA. Ecological aspects of the distribution of different autotrophic CO2 fixation pathways. Applied and Environmental Microbiology. 2011;77(6):1925-36.</a></span></span>. Six different autotrophic pathways for carbon fixation have been discovered in a variety of organisms <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3424341/">Ducat DC, Silver PA. Improving Carbon Fixation Pathways. Current opinion in chemical biology. 2012;16(3-4):337-44.</a></span></span>. The most widespread of these, is the Calvin-Benson-Bassham (CBB) cycle, found in photosynthetic eukaryotes, e.g. plants and algae, as well as in photo- and chemosynthetic bacteria <span class="reference"><span class="referencetext"><a target="blank" href="https://books.google.dk/books?id=puEsBAAAQBAJ&pg=PA21&lpg=PA21&dq=calvin+cycle+most+widespread&source=bl&ots=8QGIRwvzDj&sig=7jfO_H3MSc67XxB8xRM3nVdavdA&hl=en&sa=X&ved=0ahUKEwj64OL0-pXVAhXrbZoKHbEWCzcQ6AEINjAD#v=onepage&q=cyano&f=false">B. Bowien MG, R. Klintworth, U. Windhövel. Metabolic and Molecular Regulation of the CO2-assimilating Enzyme System in Aerobic Chemoautotrophs. Microbial Growth on C1 Compounds: Proceedings of the 5th International Symposion. 1st ed. Institute for Microbiology, Georg-August-University Göttingen, Federal Republic of Germany: Martinus Nijhoff Publishers; 1987.</a></span></span>. The Calvin cycle, as this pathway is also called, can proceed under aerobic conditions, and only three enzymes and one microcompartment involved are heterologous to the gram-negative bacteria <i>E. coli</i>, making this the most obvious choice for the implementation of a carbon fixation pathway. In contrast, the 3-hydroxypropionate pathway for | + | Carbon fixation in autotrophic organisms is responsible for the net fixation of 7×10<sup>16</sup> g carbon annually, thereby being the most imperative biosynthetic process in nature <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/?term=Berg+(2011)+Ecological+Aspects+of+the+Distribution+of+Different+Autotrophic+CO2+Fixation+Pathways">Berg IA. Ecological aspects of the distribution of different autotrophic CO2 fixation pathways. Applied and Environmental Microbiology. 2011;77(6):1925-36.</a></span></span>. Six different autotrophic pathways for carbon fixation have been discovered in a variety of organisms <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3424341/">Ducat DC, Silver PA. Improving Carbon Fixation Pathways. Current opinion in chemical biology. 2012;16(3-4):337-44.</a></span></span>. The most widespread of these, is the Calvin-Benson-Bassham (CBB) cycle, found in photosynthetic eukaryotes, e.g. plants and algae, as well as in photo- and chemosynthetic bacteria <span class="reference"><span class="referencetext"><a target="blank" href="https://books.google.dk/books?id=puEsBAAAQBAJ&pg=PA21&lpg=PA21&dq=calvin+cycle+most+widespread&source=bl&ots=8QGIRwvzDj&sig=7jfO_H3MSc67XxB8xRM3nVdavdA&hl=en&sa=X&ved=0ahUKEwj64OL0-pXVAhXrbZoKHbEWCzcQ6AEINjAD#v=onepage&q=cyano&f=false">B. Bowien MG, R. Klintworth, U. Windhövel. Metabolic and Molecular Regulation of the CO2-assimilating Enzyme System in Aerobic Chemoautotrophs. Microbial Growth on C1 Compounds: Proceedings of the 5th International Symposion. 1st ed. Institute for Microbiology, Georg-August-University Göttingen, Federal Republic of Germany: Martinus Nijhoff Publishers; 1987.</a></span></span>. The Calvin cycle, as this pathway is also called, can proceed under aerobic conditions, and only three enzymes and one microcompartment involved are heterologous to the gram-negative bacteria <i>E. coli</i>, making this the most obvious choice for the implementation of a carbon fixation pathway. In contrast, the 3-hydroxypropionate pathway for carbon fixation would require the transfer of ten heterologous genes <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/23376595">1. Mattozzi M, Ziesack M, Voges MJ, Silver PA, Way JC. Expression of the sub-pathways of the Chloroflexus aurantiacus 3-hydroxypropionate carbon fixation bicycle in E. coli: Toward horizontal transfer of autotrophic growth. Metabolic engineering. 2013;16:130-9.</a></span></span>. Furthermore, the reductive carboxylic acid cycle found in phylogenetically diverse autotrophic bacteria and archaea <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/?term=Evidence+for+Autotrophic+CO2+Fixation+via+the+Reductive+Tricarboxylic+Acid+Cycle+by+Members+of+the+%CE%B5+Subdivision+of+Proteobacteria%E2%80%A0">Hugler M, Wirsen CO, Fuchs G, Taylor CD, Sievert SM. Evidence for autotrophic CO2 fixation via the reductive tricarboxylic acid cycle by members of the epsilon subdivision of proteobacteria. J Bacteriol. 2005;187(9):3020-7.</a></span></span> and the noncyclic reductive acetyl-CoA or Wood-Ljungdahl pathway <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2646786/">Ragsdale SW, Pierce E. Acetogenesis and the Wood-Ljungdahl Pathway of CO(2) Fixation. Biochimica et biophysica acta. 2008;1784(12):1873-98.</a></span></span> require strict anaerobic conditions. <br> |
The Calvin cycle involves eleven enzymes, of which eight are intrinsic to <i>E. coli</i>. The three heterologous enzymes are RuBisCo, SBPase and PRK. The latter phosphorylates ribulose-5-phosphate to ribulose-1,5-bisphosphate. This is the substrate for RuBisCo, which catalyses the carboxylation, whereby glycerate-3-phosphate is produced. Later in the cycle, SBPase catalyses the dephosphorylation of sedoheptulose-1,7-bisphosphate to sedoheptulose-7-phosphate, which is later converted to ribulose-5-phosphate, completing the circle. The net effect of three full cycles is the conversion of three CO<sub>2</sub> molecules into one molecule glyceraldehyde-3-phosphate, which can be used for energy production via glycolysis or polysaccharide biosynthesis. Separately, these enzymes have previously been heterogeneously expressed in <i>E. coli</i> using various donor species, such as wheat <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/9758762">Dunford RP, Catley MA, Raines CA, Lloyd JC, Dyer TA. Purification of active chloroplast sedoheptulose-1,7-bisphosphatase expressed in Escherichia coli. Protein expression and purification. 1998;14(1):139-45.</a></span></span>, the algae <i>Chlamydomonas sp.</i> <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/15849430">Tamoi M, Nagaoka M, Shigeoka S. Immunological properties of sedoheptulose-1,7-bisphosphatase from Chlamydomonas sp. W80. Bioscience, biotechnology, and biochemistry. 2005;69(4):848-51.</a></span></span><span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/26828117">Vira C, Prakash G, Rathod JP, Lali AM. Cloning, expression, and purification of Chlamydomonas reinhardtii CC-503 sedoheptulose 1,7-bisphosphatase in Escherichia coli. Preparative biochemistry & biotechnology. 2016;46(8):810-4.</a></span></span>, and the cyanobacteria <i>Synechococcus</i> <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/16423843">Parikh MR, Greene DN, Woods KK, Matsumura I. Directed evolution of RuBisCO hypermorphs through genetic selection in engineered E.coli. Protein engineering, design & selection : PEDS. 2006;19(3):113-9.</a></span></span>. <br> | The Calvin cycle involves eleven enzymes, of which eight are intrinsic to <i>E. coli</i>. The three heterologous enzymes are RuBisCo, SBPase and PRK. The latter phosphorylates ribulose-5-phosphate to ribulose-1,5-bisphosphate. This is the substrate for RuBisCo, which catalyses the carboxylation, whereby glycerate-3-phosphate is produced. Later in the cycle, SBPase catalyses the dephosphorylation of sedoheptulose-1,7-bisphosphate to sedoheptulose-7-phosphate, which is later converted to ribulose-5-phosphate, completing the circle. The net effect of three full cycles is the conversion of three CO<sub>2</sub> molecules into one molecule glyceraldehyde-3-phosphate, which can be used for energy production via glycolysis or polysaccharide biosynthesis. Separately, these enzymes have previously been heterogeneously expressed in <i>E. coli</i> using various donor species, such as wheat <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/9758762">Dunford RP, Catley MA, Raines CA, Lloyd JC, Dyer TA. Purification of active chloroplast sedoheptulose-1,7-bisphosphatase expressed in Escherichia coli. Protein expression and purification. 1998;14(1):139-45.</a></span></span>, the algae <i>Chlamydomonas sp.</i> <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/15849430">Tamoi M, Nagaoka M, Shigeoka S. Immunological properties of sedoheptulose-1,7-bisphosphatase from Chlamydomonas sp. W80. Bioscience, biotechnology, and biochemistry. 2005;69(4):848-51.</a></span></span><span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/26828117">Vira C, Prakash G, Rathod JP, Lali AM. Cloning, expression, and purification of Chlamydomonas reinhardtii CC-503 sedoheptulose 1,7-bisphosphatase in Escherichia coli. Preparative biochemistry & biotechnology. 2016;46(8):810-4.</a></span></span>, and the cyanobacteria <i>Synechococcus</i> <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/16423843">Parikh MR, Greene DN, Woods KK, Matsumura I. Directed evolution of RuBisCO hypermorphs through genetic selection in engineered E.coli. Protein engineering, design & selection : PEDS. 2006;19(3):113-9.</a></span></span>. <br> | ||
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In order to engineer <i>E. coli</i> in the outer chamber to turn atmospheric CO<sub>2</sub> into cellulose, the carbon first needs to be fixated by the bacteria. This requires the heterologous expression of the genes encoding the three enzymes RuBisCo, SBPase, and PRK. In correspondence with the <a href="https://2014.igem.org/Team:Bielefeld-CeBiTec" target="_blank">2014 Bielefeld iGEM team</a>, who worked with a similar subpart of their project, we discussed the cloning of these genes and received two crucial parts. The first of this was <a href="http://parts.igem.org/Part:BBa_K1465214" target="_blank">BBa_K1465214</a>, containing RubisCO from <i>Halothiobacillus neapolitanus</i> and PRK from <i>Synechococcus elongatus</i> under the control of a composite promoter controllable by IPTG. The second was <a href="http://parts.igem.org/Part:BBa_K1465228" target="_blank">BBa_K1465228</a>, which contained SBPase from <i>Bacillus methanolicus</i>. Through the concurrent expression of these parts in <i>E. coli</i>, all enzymes required to fixate CO<sub>2</sub> through the Calvin cycle were present in the cells. | In order to engineer <i>E. coli</i> in the outer chamber to turn atmospheric CO<sub>2</sub> into cellulose, the carbon first needs to be fixated by the bacteria. This requires the heterologous expression of the genes encoding the three enzymes RuBisCo, SBPase, and PRK. In correspondence with the <a href="https://2014.igem.org/Team:Bielefeld-CeBiTec" target="_blank">2014 Bielefeld iGEM team</a>, who worked with a similar subpart of their project, we discussed the cloning of these genes and received two crucial parts. The first of this was <a href="http://parts.igem.org/Part:BBa_K1465214" target="_blank">BBa_K1465214</a>, containing RubisCO from <i>Halothiobacillus neapolitanus</i> and PRK from <i>Synechococcus elongatus</i> under the control of a composite promoter controllable by IPTG. The second was <a href="http://parts.igem.org/Part:BBa_K1465228" target="_blank">BBa_K1465228</a>, which contained SBPase from <i>Bacillus methanolicus</i>. Through the concurrent expression of these parts in <i>E. coli</i>, all enzymes required to fixate CO<sub>2</sub> through the Calvin cycle were present in the cells. | ||
<br> | <br> | ||
− | The first approach was to assemble both parts on one plasmid by molecular cloning, as shown on | + | The first approach was to assemble both parts on one plasmid by molecular cloning, as shown on Figure 1. In doing this, it was discovered that the <a href="http://parts.igem.org/Part:BBa_K1465214" target="_blank">BBa_K1465214</a> part was missing roughly 1 kbp when digested with standard restriction enzymes with recognition sites within the BioBrick prefix and suffix. Sequencing of the part revealed that the part was missing the entire promoter sequence of 1239 bp. Consequently, the assembly of the parts additionally required the cloning of a promoter. For this purpose, the Tac-promoter (Ptac) from the part <a href="http://parts.igem.org/Part:BBa_K864400" target="_blank">BBa_K864400</a> was chosen, as this is commonly used to overexpress genes in <i>E. coli</i>. With the objective to place the two Calvin cycle parts on different vectors, it was attempted to clone Ptac in front of both parts. However, this did not succeed and it was decided to prioritise other aspects of the project and therefore keep this part theoretical henceforth. |
<br> | <br> | ||
<b>Implementing the Carboxysome in <i>E. coli</i> to Increase Carbon Fixation Efficiency</b> | <b>Implementing the Carboxysome in <i>E. coli</i> to Increase Carbon Fixation Efficiency</b> | ||
<br> | <br> | ||
− | The implementation of the microcompartment carboxysome in the test organism can increase the efficiency of the carbon fixation process substantially. As for the Calvin cycle parts, we corresponded with the <a href="https://2014.igem.org/Team:Bielefeld-CeBiTec" target="_blank">2014 Bielefeld iGEM team</a> on their experience of the implementation of the carboxysome, and received the two parts that together contained the <i>cso</i> operon from <i>Halothiobacillus neapolitanus.</i> These parts were <a href="http://parts.igem.org/Part:BBa_K1465204" target="_blank">BBa_K1465204</a>, containing <i>csoS2</i>, and <a href="http://parts.igem.org/Part:BBa_K1465209" target="_blank">BBa_K1465209</a>, containing <i>csoS3</i>, <i>csoS14</i>, and <i>csoS1D</i>. As part of the optimisation, we aimed to combine these parts into one part containing the entire <i>cso</i> operon, as shown on | + | The implementation of the microcompartment carboxysome in the test organism can increase the efficiency of the carbon fixation process substantially. As for the Calvin cycle parts, we corresponded with the <a href="https://2014.igem.org/Team:Bielefeld-CeBiTec" target="_blank">2014 Bielefeld iGEM team</a> on their experience of the implementation of the carboxysome, and received the two parts that together contained the <i>cso</i> operon from <i>Halothiobacillus neapolitanus.</i> These parts were <a href="http://parts.igem.org/Part:BBa_K1465204" target="_blank">BBa_K1465204</a>, containing <i>csoS2</i>, and <a href="http://parts.igem.org/Part:BBa_K1465209" target="_blank">BBa_K1465209</a>, containing <i>csoS3</i>, <i>csoS14</i>, and <i>csoS1D</i>. As part of the optimisation, we aimed to combine these parts into one part containing the entire <i>cso</i> operon, as shown on Figure 1. Furthermore, a promoter was required to drive the gene expression. For this purpose, Ptac was chosen, as for the genes encoding the Calvin cycle enzymes. </p> |
<br> | <br> | ||
<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/8/83/T--SDU-Denmark--carbon-fixation-genes.svg" type="image/svg+xml" style="width:100%;"></object></div> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/8/83/T--SDU-Denmark--carbon-fixation-genes.svg" type="image/svg+xml" style="width:100%;"></object></div> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 1.</b> The envisaged design of the carboxysomal genes, encoded in the composite part, <a href="http://parts.igem.org/Part:BBa_K2449030" target="_blank">BBa_K2449030</a>, under control of the Tac-promoter.</p></div><br class="noContent"> |
<p>We succeeded in assembling both carboxysome parts in the composite part, <a href="http://parts.igem.org/Part:BBa_K2449030" target="_blank">BBa_K2449030</a>, but for some inexplicable reason, this composite part likewise emerged difficult to clone with the Tac-promoter. Therefore, it was decided to focus at other aspects of the project and, as for the Calvin cycle part, keep this part theoretical henceforth. | <p>We succeeded in assembling both carboxysome parts in the composite part, <a href="http://parts.igem.org/Part:BBa_K2449030" target="_blank">BBa_K2449030</a>, but for some inexplicable reason, this composite part likewise emerged difficult to clone with the Tac-promoter. Therefore, it was decided to focus at other aspects of the project and, as for the Calvin cycle part, keep this part theoretical henceforth. | ||
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− | <div style="text-align:center;"><p style="font-size:14px;"><i><a href="#project-design">Click here to return to the | + | <div style="text-align:center;"><p style="font-size:14px;"><i><a href="#project-design">Click here to return to the Project Design overview.</a></i></p></div> |
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− | <p class="P-Larger"><b> | + | <p class="P-Larger"><b>Introduction</b></p><br> |
<p> | <p> | ||
<span class="highlighted">Bacterial cellulose is one of the most abundant biopolymers produced by different species of gram-negative bacteria</span>, especially by <i>Acetobactors</i>. <i>Glucoacetobacter xylinus</i> is a bacterial species, which produces cellulose in large quantities of high quality <span class="reference"><span class="referencetext"><a target="blank" href="https://doi.org/10.1007/s10570-013-9994-3">Lin, SP., Loira Calvar, I., Catchmark, J.M. et al. Cellulose (2013) 20: 2191.</a></span></span>. Cellulose is produced from the resource glucose-6-phosphate. This phosphorylated glucose is a key intermediate in the core carbon metabolism of bacteria given its importance in glycolysis, gluconeogenesis and pentose phosphate pathway <span class="reference"><span class="referencetext"><a target="blank" href="https://www.amazon.com/Prescotts-Microbiology-Joanne-Willey/dp/0073402400">Joanne Willey LS, Christopher J. Woolverton. Prescott’s Microbiology. 9th edition 2014.</a></span></span>. Even though the pathway, where glucose and glucose-6-phosphate is converted into cellulose, only includes few steps, it requires a great amount of energy. Not only does the cell spend energy on forming UDP-glucose for cellulose biosynthesis, it also uses glucose, which otherwise would have contributed to generation of ATP <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/27247386">Florea M, Hagemann H, Santosa G, Abbott J, Micklem CN, Spencer-Milnes X, et al. Engineering control of bacterial cellulose production using a genetic toolkit and a new cellulose-producing strain. Proceedings of the National Academy of Sciences of the United States of America. 2016;113(24):E3431-40.</a></span></span>. | <span class="highlighted">Bacterial cellulose is one of the most abundant biopolymers produced by different species of gram-negative bacteria</span>, especially by <i>Acetobactors</i>. <i>Glucoacetobacter xylinus</i> is a bacterial species, which produces cellulose in large quantities of high quality <span class="reference"><span class="referencetext"><a target="blank" href="https://doi.org/10.1007/s10570-013-9994-3">Lin, SP., Loira Calvar, I., Catchmark, J.M. et al. Cellulose (2013) 20: 2191.</a></span></span>. Cellulose is produced from the resource glucose-6-phosphate. This phosphorylated glucose is a key intermediate in the core carbon metabolism of bacteria given its importance in glycolysis, gluconeogenesis and pentose phosphate pathway <span class="reference"><span class="referencetext"><a target="blank" href="https://www.amazon.com/Prescotts-Microbiology-Joanne-Willey/dp/0073402400">Joanne Willey LS, Christopher J. Woolverton. Prescott’s Microbiology. 9th edition 2014.</a></span></span>. Even though the pathway, where glucose and glucose-6-phosphate is converted into cellulose, only includes few steps, it requires a great amount of energy. Not only does the cell spend energy on forming UDP-glucose for cellulose biosynthesis, it also uses glucose, which otherwise would have contributed to generation of ATP <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/27247386">Florea M, Hagemann H, Santosa G, Abbott J, Micklem CN, Spencer-Milnes X, et al. Engineering control of bacterial cellulose production using a genetic toolkit and a new cellulose-producing strain. Proceedings of the National Academy of Sciences of the United States of America. 2016;113(24):E3431-40.</a></span></span>. | ||
<br> | <br> | ||
− | <span class="highlighted">The ability for <i>G. xylinus</i> to produce cellulose nanofibers from UDP-glucose, crystallize, and secrete it, is controlled by genes in the Acetobacter cellulose synthase (acs) operon <i>acsABCD</i></span>. This operon encodes four different proteins: AcsA, AcsB, AcsC and AcsD. A dimer, known as AcsAB, is formed by a catalytic domain, AcsA, and a regulatory domain, AcsB. This dimer is responsible for synthesising the cellulose nanofibers from UDP-glucose, whereas AcsC and AcsD secretes cellulose and forms an interconnected cellulose pellicle around the cells <span class="reference"><span class="referencetext"><a target="blank" href="https://link-springer-com.proxy1-bib.sdu.dk/article/10.1007%2Fs10570-014-0521-y">Mehta K, et al. Characterization of an acsD disruption mutant provides additional evidence for the hierarchical cell-directed self-assembly of cellulose in Gluconacetobacter xylinus. Cellulose. 2014;22:119–137.</a></span></span>, as illustrated in | + | <span class="highlighted">The ability for <i>G. xylinus</i> to produce cellulose nanofibers from UDP-glucose, crystallize, and secrete it, is controlled by genes in the Acetobacter cellulose synthase (acs) operon <i>acsABCD</i></span>. This operon encodes four different proteins: AcsA, AcsB, AcsC and AcsD. A dimer, known as AcsAB, is formed by a catalytic domain, AcsA, and a regulatory domain, AcsB. This dimer is responsible for synthesising the cellulose nanofibers from UDP-glucose, whereas AcsC and AcsD secretes cellulose and forms an interconnected cellulose pellicle around the cells <span class="reference"><span class="referencetext"><a target="blank" href="https://link-springer-com.proxy1-bib.sdu.dk/article/10.1007%2Fs10570-014-0521-y">Mehta K, et al. Characterization of an acsD disruption mutant provides additional evidence for the hierarchical cell-directed self-assembly of cellulose in Gluconacetobacter xylinus. Cellulose. 2014;22:119–137.</a></span></span>, as illustrated in Figure 6. |
</p><br> | </p><br> | ||
<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/1/18/T--SDU-Denmark--cellulose-biosynthesis.svg" type="image/svg+xml" style="width:85%;"></object></div> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/1/18/T--SDU-Denmark--cellulose-biosynthesis.svg" type="image/svg+xml" style="width:85%;"></object></div> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 6.</b> The AcsAB dimer synthesises cellulose nanofibers. AcsC and AcsD mediate the secretion and formation of an interconnected cellulose pellicle.</p></div><br class="noContent"> |
<p>Other genera, including some <i>E. coli</i> strains, secrete cellulose as a component of their biofilm. Even though cellulose biosynthesis is intrinsic to <i>E. coli</i>, the quantity of the production is incomparable to cellulose biosynthesis in <i>G. xylinus</i>. Indigenously, <i>E. coli</i> is not capable of degrading cellulose into a metabolisable energy source <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/26452465">Gao D, Luan Y, Wang Q, Liang Q, Qi Q. Construction of cellulose-utilizing Escherichia coli based on a secretable cellulase. Microbial Cell Factories. 2015;14:159.</a></span></span>. However, if this structural and water-holding polymer is enzymatically degraded, first into cellobiose and then to glucose residues, the cellulose polymer is a potent source of energy <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/17244702"> Arai T, Matsuoka S, Cho HY, | <p>Other genera, including some <i>E. coli</i> strains, secrete cellulose as a component of their biofilm. Even though cellulose biosynthesis is intrinsic to <i>E. coli</i>, the quantity of the production is incomparable to cellulose biosynthesis in <i>G. xylinus</i>. Indigenously, <i>E. coli</i> is not capable of degrading cellulose into a metabolisable energy source <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/26452465">Gao D, Luan Y, Wang Q, Liang Q, Qi Q. Construction of cellulose-utilizing Escherichia coli based on a secretable cellulase. Microbial Cell Factories. 2015;14:159.</a></span></span>. However, if this structural and water-holding polymer is enzymatically degraded, first into cellobiose and then to glucose residues, the cellulose polymer is a potent source of energy <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/17244702"> Arai T, Matsuoka S, Cho HY, | ||
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<p> | <p> | ||
<b>Optimised Cellulose Biosynthesis in <i>E. coli</i></b><br> | <b>Optimised Cellulose Biosynthesis in <i>E. coli</i></b><br> | ||
− | To enhance the cellulose biosynthesis, parts containing the coding sequence of the Cellulose Synthase enzyme were cloned into the <i>E. coli</i> strain MG1655. The original idea was to clone the entire cellulose synthase operon <i>acsABCD</i> into one vector under control of the Ptac, as seen in | + | To enhance the cellulose biosynthesis, parts containing the coding sequence of the Cellulose Synthase enzyme were cloned into the <i>E. coli</i> strain MG1655. The original idea was to clone the entire cellulose synthase operon <i>acsABCD</i> into one vector under control of the Ptac, as seen in Figure 1. With a plasmid with a total length over 9000 bp, the cloning emerged difficult. After several unsuccessful attempts, a different approach was sought. |
</p><br> | </p><br> | ||
<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/5/5d/T--SDU-Denmark--cellulose-production-genes.svg" type="image/svg+xml" style="width:95%;"></object></div> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/5/5d/T--SDU-Denmark--cellulose-production-genes.svg" type="image/svg+xml" style="width:95%;"></object></div> | ||
− | <br><div class="figure-text"><p><b>Figure | + | <br><div class="figure-text"><p><b>Figure 1.</b> The <i>acsABCD</i> operon controlled by Ptac cloned into one high copy vector.</p></div><br class="noContent"> |
<p>In this design, it was attempted to implement the <i>acsABCD</i> operon into <i>E. coli</i> MG1655 on two separate vectors, with both parts controlled by Ptac<a href="http://parts.igem.org/Part:BBa_K864400" target="_blank">BBa_K864400</a>, ensuring equal expression levels of the parts. The AcsAB dimer, encoded in the part <a href="http://parts.igem.org/Part:BBa_K1321334" target="_blank">BBa_K1321334</a>, was attempted to be inserted into the vector pSB1C3. The part <a href="http://parts.igem.org/Part:BBa_K1321335" target="_blank">BBa_K1321335</a>, containing AcsC and AcsD, was inserted into the vector pSB1A3. Several combinations of the two parts and different vectors carrying different resistance cassettes were attempted, but unfortunately without success. Correspondence with a supervisor from the <a href="https://2014.igem.org/Team:Imperial" target="_blank">Imperial College London team</a>, revealed that cloning with these parts had emerged difficult for them as well. Due to time constraints, it was decided to prioritise other aspects of the project and therefore keep this part theoretical henceforth. | <p>In this design, it was attempted to implement the <i>acsABCD</i> operon into <i>E. coli</i> MG1655 on two separate vectors, with both parts controlled by Ptac<a href="http://parts.igem.org/Part:BBa_K864400" target="_blank">BBa_K864400</a>, ensuring equal expression levels of the parts. The AcsAB dimer, encoded in the part <a href="http://parts.igem.org/Part:BBa_K1321334" target="_blank">BBa_K1321334</a>, was attempted to be inserted into the vector pSB1C3. The part <a href="http://parts.igem.org/Part:BBa_K1321335" target="_blank">BBa_K1321335</a>, containing AcsC and AcsD, was inserted into the vector pSB1A3. Several combinations of the two parts and different vectors carrying different resistance cassettes were attempted, but unfortunately without success. Correspondence with a supervisor from the <a href="https://2014.igem.org/Team:Imperial" target="_blank">Imperial College London team</a>, revealed that cloning with these parts had emerged difficult for them as well. Due to time constraints, it was decided to prioritise other aspects of the project and therefore keep this part theoretical henceforth. | ||
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− | <div style="text-align:center;"><p style="font-size:14px;"><i><a href="#project-design">Click here to return to the | + | <div style="text-align:center;"><p style="font-size:14px;"><i><a href="#project-design">Click here to return to the Project Design overview.</a></i></p></div> |
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<div style="text-align:center;"><p><span class="reference-2">Project Overview<span class="referencetext-2"><object data="https://static.igem.org/mediawiki/2017/0/09/T--SDU-Denmark--project-overview-cellulose-breakdown.svg" style="width:100%;" type="image/svg+xml"></object></span></span></p></div><br> | <div style="text-align:center;"><p><span class="reference-2">Project Overview<span class="referencetext-2"><object data="https://static.igem.org/mediawiki/2017/0/09/T--SDU-Denmark--project-overview-cellulose-breakdown.svg" style="width:100%;" type="image/svg+xml"></object></span></span></p></div><br> | ||
− | + | <p class="P-Larger"><b><span class="highlighted">Introduction</span></b></p> | |
− | + | <br> | |
− | <p> | + | <p class=""> |
− | Cellulose is a natural biopolymer used for a | + | Cellulose is a natural biopolymer used for a vast variety of biological purposes and it is most commonly found in plants, where it serves as the main structural component. Since plants are primary producers, many organisms of the Earth’s ecosystems have adapted accordingly<span class="reference"><span class="referencetext"><a target="blank" href="http://mmbr.asm.org/content/66/3/506.long"> Lynd |
+ | LR, Weimer PJ, van Zyl WH, Pretorius IS. Microbial Cellulose Utilization: | ||
+ | Fundamentals and Biotechnology. Microbiology and Molecular Biology Reviews. | ||
+ | 2002;66(3):506-77.</a></span></span>. One of the key evolutionary features for the primary consumers, was the development of the ability to <span class="highlighted">degrade cellulose into glucose, which could then be used as a cellular fuel. </span>A simple organism, able to efficiently do so, is the <i>Cellulomonas fimi</i>, which converts cellulose to glucose in a two-step process, with cellobiose as the intermediate<span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3403577/"> Jung | ||
+ | SK, Parisutham V, Jeong SH, Lee SK. Heterologous Expression of Plant Cell Wall | ||
+ | Degrading Enzymes for Effective Production of Cellulosic Biofuels. Journal of Biomedicine and Biotechnology. 2012;2012.</a></span></span>. | ||
</p> | </p> | ||
+ | <br> | ||
<br class="noContent"> | <br class="noContent"> | ||
<br class="noContent"> | <br class="noContent"> | ||
− | + | <p class=""> | |
− | + | ||
− | <p> | + | |
<b>Breakdown of Cellulose to Cellobiose</b><br> | <b>Breakdown of Cellulose to Cellobiose</b><br> | ||
− | Cellulose is a long polysaccharide consisting of β-1,4 linked D-glucose units | + | Cellulose is a long polysaccharide consisting of β-1,4-linked <small>D</small>-glucose units and many organisms, including <span class="highlighted"><i>E. coli</i>, lack the enzymes able to degrade these strong β-linkages. To overcome this, the <i>C. fimi</i> has developed two cellulases, namely the endo-β-1,4-glucanase and exo-β-1,4-glucanase, respectively encoded by the <i>cenA</i> and <i>cex</i> genes <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3403577/"> Jung |
+ | SK, Parisutham V, Jeong SH, Lee SK. Heterologous Expression of Plant Cell Wall | ||
+ | Degrading Enzymes for Effective Production of Cellulosic Biofuels. Journal of Biomedicine and Biotechnology. 2012;2012.</a></span></span>.</span> The endoglucanase is able to randomly degrade the amorphous structure of cellulose, thereby allowing the exoglucanase to cleave the β-1,4 linkages at every other <small>D</small>-glucose unit. Thus, disaccharides are released in the form of cellobiose <span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/9134758/"> Lam TL, Wong RS, Wong WK. | ||
+ | Enhancement of extracellular production of a Cellulomonas fimi exoglucanase in | ||
+ | Escherichia coli by the reduction of promoter strength. Enzyme and microbial | ||
+ | technology. 1997;20(7):482-8.</a></span></span>, as illustrated in Figure 7. <span class="highlighted">Cellulose itself is too large to be transported across the bacterial cell membrane</span>, and therefore, the breakdown of cellulose into cellobiose must take place in the extracellular fluid. | ||
</p> | </p> | ||
− | + | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/e/ed/T--SDU-Denmark--cellulose-to-cellobiose.svg" type="image/svg+xml" style="width:80%;"></object></div> | |
− | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/e/ed/T--SDU-Denmark--cellulose-to-cellobiose.svg" type="image/svg+xml" style="width:80%;"></object></div>< | + | <div class="figure-text"><p><b>Figure 7.</b> Degradation of the β-1,4 linkages in cellulose mediated by the enzymes endo-β-1,4-glucanase and exo-β-1,4-glucanase, thereby creating cellobiose. |
+ | </p></div> | ||
<br class="noContent"> | <br class="noContent"> | ||
− | < | + | <p class=""> |
− | + | ||
− | + | ||
<b>The α-Hemolysin Transport System</b><br> | <b>The α-Hemolysin Transport System</b><br> | ||
− | The ɑ-hemolysin transport system is an ABC transporter complex | + | The ɑ-hemolysin transport system is an <span class="highlighted">ABC transporter complex consisting of three proteins, namely the outer membrane protein TolC, hemolysin B (HlyB), and hemolysin D (HlyD)</span><span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/11755084"> Gentschev I, Dietrich G, Goebel W. The E. coli |
+ | alpha-hemolysin secretion system and its use in vaccine development. Trends in | ||
+ | microbiology. 2002;10(1):39-45.</a></span></span>, which can effectively transport intracellular hemolysin A (HlyA) to the extracellular fluid. Utilising a linker peptide, the protein of interest can be fused with HlyA. <span class="highlighted">Once a protein is HlyA-tagged, it can be recognized by the ATP-binding cassette HlyB, which will initiate transportation of the HlyA-tagged protein to the extracellular fluid, as seen in Figure 8<span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/11755084"> Gentschev I, Dietrich G, Goebel W. The E. coli | ||
+ | alpha-hemolysin secretion system and its use in vaccine development. Trends in | ||
+ | microbiology. 2002;10(1):39-45.</a></span></span><span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/22239833"> Su | ||
+ | L, Chen S, Yi L, Woodard RW, Chen J, Wu J. Extracellular overexpression of | ||
+ | recombinant Thermobifida fusca cutinase by alpha-hemolysin secretion system in | ||
+ | E. coli BL21(DE3). Microbial Cell Factories. 2012;11:8.</a></span></span></span>. | ||
</p> | </p> | ||
− | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/7/7b/T--SDU-Denmark--hlyb-hlyd-transporter.svg" type="image/svg+xml" style="width: | + | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/7/7b/T--SDU-Denmark--hlyb-hlyd-transporter.svg" type="image/svg+xml" style="width:80%;"></object></div> |
+ | <div class="figure-text"><p><b>Figure 8.</b> The enzymes encoded by the <i>cenA</i> and <i>cex</i> genes are linked to HlyA. HlyB recognises HlyA and initiates transportation of the HlyA-tagged protein from the cytosol to the extracellular fluid | ||
+ | </p></div> | ||
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<b>Uptake of Cellobiose</b><br> | <b>Uptake of Cellobiose</b><br> | ||
− | While cellulose is too large to be pass the cell membrane, transportation of cellobiose is a common feature found in many organisms. An example is <i>E. coli</i>, which utilises the membrane protein lactose permease (LacY) | + | While cellulose is too large to be pass the cell membrane, <span class="highlighted">transportation of cellobiose is a common feature found in many organisms. An example is <i>E. coli</i>,</span> which utilises the membrane protein lactose permease (LacY)<span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3294459/"> Sekar R, Shin HD, Chen R. Engineering Escherichia coli Cells for Cellobiose Assimilation through a |
+ | Phosphorolytic Mechanism. Applied and Environmental Microbiology. | ||
+ | 2012;78(5):1611-4.</a></span></span>, whereby the cellobiose is enzymatically catabolised in the cytosol. | ||
</p> | </p> | ||
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− | + | <b>Degradation of Cellobiose to Glucose</b><br> | |
− | <p> | + | Through evolutionary events, many organisms have developed the ability to express enzymes, capable of breaking the β-linkage in cellobiose. <span class="highlighted"><i>E. coli</i> expresses the periplasmic β-glucosidase encoded by the <i>bglX</i> gene, which is known to have said feature, hydrolysing the cellobiose β-linkage<span class="reference"><span class="referencetext"><a target="blank" href=" http://www.uniprot.org/uniprot/P33363">UniProt entry for <i>bglX</i></a></span></span>.</span> <i>Saccharophagus degradans</i> expresses <span class="highlighted">a different enzyme, which efficiently cleaves the β-linkage in cellobiose, namely cellobiose phosphorylase encoded by the <i>cep94A</i> gene.</span> This enzyme phosphorylates the cellobiose at its β-linkage, resulting in the degradation of cellobiose to <small>D</small>-glucose and α-<small>D</small>-glucose-1-phosphate<span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3294459/"> Sekar R, Shin HD, Chen R. Engineering Escherichia coli Cells for Cellobiose Assimilation through a |
− | <b> | + | Phosphorolytic Mechanism. Applied and Environmental Microbiology. |
− | Through evolutionary events, many organisms have developed the ability to express enzymes, capable of breaking the β-linkage in cellobiose. <i>E. coli</i> expresses the periplasmic β-glucosidase encoded by the <i>bglX</i> gene, which is known to have said feature, | + | 2012;78(5):1611-4.</a></span></span>, as seen in Figure 9. |
</p> | </p> | ||
− | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/7/7b/T--SDU-Denmark--cellobiose-to-glucose.svg" type="image/svg+xml" style="width:80%;"></object></div>< | + | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/7/7b/T--SDU-Denmark--cellobiose-to-glucose.svg" type="image/svg+xml" style="width:80%;"></object></div> |
− | + | <div class="figure-text"><p><b>Figure 9. </b>Phosphorylation of the β-1,4-linkages in cellobiose by the enzyme cellobiose phosphorylase, thereby producing <small>D</small>-glucose and α-<small>D</small>-glucose-1-phosphate. | |
+ | </p></div> | ||
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− | <p> | + | |
<b>Cellulose to Cellobiose</b><br> | <b>Cellulose to Cellobiose</b><br> | ||
− | In the endeavour to engineer <i>E. coli</i> to utilise cellulose as it’s only carbon source, inspiration was drawn from the <a href="https://2008.igem.org/Team:Edinburgh" target="_blank">Edinburgh 2008 iGEM team</a> project, who developed two BioBricks containing the <i>cenA</i> and <i>cex</i> genes. In this project, the α-hemolysin transport system was utilised by creating HlyA-tagged endo- and exo-β-1,4- | + | In the endeavour to engineer <i>E. coli</i> to utilise cellulose as it’s only carbon source, inspiration was drawn from the <a href="https://2008.igem.org/Team:Edinburgh" target="_blank">Edinburgh 2008 iGEM team</a> project, who developed two BioBricks containing the <i>cenA</i> and <i>cex</i> genes. In this project, the α-hemolysin transport system was utilised by creating HlyA-tagged endo- and exo-β-1,4-glucanases, using a peptide linker. To implement this system in <i>E. coli</i>, heterogeneous expression of <i>hlyB</i>, <i>hlyD</i>, <i>cenA-hlyA</i> and <i>cex-hlyA</i> was required. |
<br> | <br> | ||
− | To achieve this, DNA synthesis of <i>cenA</i> and <i>cex</i> was ordered, each tagged with HlyA. The genes encoding HlyB and HlyD were retrieved from the part <a href="http://parts.igem.org/Part:BBa_K1166002" target="_blank">BBa_K1166002</a> by phusion PCR. Using the resulting PCR product, the following construct was composed for the degradation of cellulose into cellobiose, as illustrated | + | To achieve this, DNA synthesis of <i>cenA</i> and <i>cex</i> was ordered, each tagged with HlyA. The genes encoding HlyB and HlyD were retrieved from the part <a href="http://parts.igem.org/Part:BBa_K1166002" target="_blank">BBa_K1166002</a> by phusion PCR. Using the resulting PCR product, the following construct was composed for the degradation of cellulose into cellobiose, as illustrated in Figure 10. |
− | </p> | + | </p> |
− | + | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/7/7a/T--SDU-Denmark--cex-cena-hlybd-construct.svg" type="image/svg+xml" style="width:80%;"></object></div> | |
− | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/7/7a/T--SDU-Denmark--cex-cena-hlybd-construct.svg" type="image/svg+xml" style="width: | + | <div class="figure-text"><p><b>Figure 10. </b><a href="http://parts.igem.org/Part:BBa_K2449026" target="_blank">BioBrick</a>, containing the genes <i>cenA</i>, <i>cex</i>, <i>hlyB</i>, and <i>hlyD</i> controlled by PenI-regulated promoters. |
+ | </p></div> | ||
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− | <p> | + | <b>Cellobiose to Glucose</b><br> |
− | <b> | + | The <a href="https://2011.igem.org/Team:Edinburgh" target="_blank">Edinburgh 2011 iGEM team</a> team created a BioBrick with the <i>bglX</i> gene, which is endogenous to <i>E. coli</i>, in the endeavour to increase the efficiency of the degradation of cellobiose to glucose. However, it seems that the enzymatic activity of the periplasmic β-glucosidase has faded as a result of evolution, rendering <i>E. coli</i> incapable of surviving solely on cellobiose. Thus, even though <i>E. coli</i> can absorp cellobiose, it is not able to survive with this as it’s only carbon source. |
− | The <a href="https://2011.igem.org/Team:Edinburgh" target="_blank">Edinburgh 2011 iGEM team</a> team created a BioBrick | + | |
<br> | <br> | ||
− | + | As a solution to this, a part containing the <i>cep94A</i> gene was synthesised, with the intend to enable <i>E. coli</i> to survive solely on cellobiose. Thus, a construct containing <i>cep94A</i> controlled by a LacI-regulated promoter, was composed, as illustrated in Figure 11. | |
− | </p>< | + | |
+ | </p> | ||
+ | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/1/1a/T--SDU-Denmark--cep94-construct.svg" type="image/svg+xml" style="width:60%;"></object></div> | ||
+ | <div class="figure-text"><p><b>Figure 11.</b> <a href="http://parts.igem.org/Part:BBa_K2449004" target="_blank">BioBrick</a> comprising <i>cep94A</i> controlled by a LacI-regulated promoter. This part was cloned into both a high and low copy vector. | ||
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+ | <div style="text-align:center;"><p style="font-size:14px;"><i><a href="#project-design">Click here to return to the Project Design overview.</a></i></p></div> | ||
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− | + | <p class="P-Larger"><b><span class="highlighted">Introduction</span></b></p> | |
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+ | <b>Microbial fuel cell</b><br> | ||
+ | Electrochemical devices, such as batteries and fuel cells, are broadly used in electronics to convert chemical energy into electrical energy. <span class="highlighted">A Microbial Fuel Cell (MFC) is an open system electrochemical device</span>, consisting of two chambers; an anode chamber and a cathode chamber, which are separated by a proton exchange membrane, as illustrated in Figure 12. Both the anode and the cathode in an MFC can use various forms of graphite as base material and in the anode chamber, <span class="highlighted">microbes are utilised as catalysts to convert organic matter into metabolic products, protons, and electrons <span class="reference"><span class="referencetext"><a target="blank" href="http://www.wiley.com//legacy/wileychi/li1/">Khanal YLaSK. Microbial Fuel Cells, Capter 19. In: Khanal. EbYLaSK, editor. Bioenergy: Principles and Applications. First Edition ed: Published 2017 by John Wiley & Sons, Inc.; 2016.</a></span></span></span>. This is carried out through metabolic pathways such as glycolysis, thereby generating ATP needed to maintain cellular life. This metabolic pathway also releases electrons, which are carried by NAD<sup>+</sup> in its reduced form, NADH. | ||
+ | </p> | ||
<div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/e/ea/T--SDU-Denmark--microbial-fuel-cell.svg" type="image/svg+xml" style="width:80%;"></object></div> | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/e/ea/T--SDU-Denmark--microbial-fuel-cell.svg" type="image/svg+xml" style="width:80%;"></object></div> | ||
− | + | <div class="figure-text"><p><b>Figure 12.</b> A microbial fuel cell utilising glucose as substrate. The glucose is consumed to protons, electrons, and CO<sub>2</sub>. The electrons are transferred to the anode while the protons diffuse over the proton exchange membrane. A gradient causes the electrons to flow through an external load to the cathode, which generates an electrical current. | |
− | <br><p> | + | </p></div> |
− | Under aerobic conditions, the generated NADH will deliver its electron as part of the electron transfer chain, | + | <br> |
+ | <p> | ||
+ | Under aerobic conditions, the generated NADH will deliver its electron as part of the electron transfer chain, thereby returning to its oxidised form NAD<sup>+</sup>. Under <span class="highlighted">anaerobic conditions</span> the electron transport chain will be unable to continue, which will cause the generated NADH to accumulate, and as a consequence, the concentration of available NAD<sup>+</sup> for glycolysis will decrease. This will drive the cell to carry out other metabolic pathways, such as fermentation, in order to maintain its ATP levels. Instead, the accumulating NADH generated <span class="highlighted">under anaerobic conditions, can be utilised to drive an electrical current by depositing the retrieved electrons to an anode coupled with an appropriate cathode</span>. The cathode catalyst in an MFC will usually catalyse the reaction of 2 H<sup>+</sup> + ½ O<sub>2</sub> per H<sub>2</sub>O. <span class="highlighted">The transfer of electrons from NADH to the anode can be executed in three different ways, as shown in Figure 13; redox shuttles, direct contact electron transfer, and bacterial nanowires</span><span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pubmed/16999087"> Logan BE, Hamelers B, Rozendal R, Schroder U, Keller J, Freguia S, et al. Microbial fuel cells: methodology and technology. Environmental science & technology. 2006;40(17):5181-92.</a></span></span><span class="reference"><span class="referencetext"><a target="blank" href="http://www.wiley.com//legacy/wileychi/li1/">Khanal YLaSK. Microbial Fuel Cells, Capter 19. In: Khanal. EbYLaSK, editor. Bioenergy: Principles and Applications. First Edition ed: Published 2017 by John Wiley & Sons, Inc.; 2016.</a></span></span>.</p> | ||
+ | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/5/54/T--SDU-Denmark--electron-shuttle.svg" type="image/svg+xml" style="width:80%;"></object></div> | ||
+ | <div class="figure-text"><p><b>Figure 13.</b> Three different ways to transfer electrons from microorganisms to an anode. a) Transfer of electrons to the anode using a redox shuttle.Two different types of redox shuttles exit: One going through the membrane and another receiving electrons from membrane proteins. b) Transfer of electrons to the anode by direct contact. c) Electrons are carried from the inside the cell, directly to the anode through nanowires. | ||
+ | </p></div> | ||
+ | <br> | ||
+ | <p> | ||
+ | The redox shuttles use extracellular electron mediators, which hold the advantage of not being limited by the surface area of the anode, although it is restricted by the slow diffusion of the extracellular mediators. The direct contact electron transfer is, in contrast to the redox shuttles, strongly limited by the surface area of the anode, but the membrane bound cytochromes that are in direct contact with the anode, rapidly deliver the electrons. <span class="highlighted">Bacterial nanowires are known to efficiently transfer electrons</span>, as for the direct contact electron transfer. However, bacterial nanowires are not as strictly limited by the surface area of the anode as the direct contact electron transfer. This is due to the ability of bacterial nanowires to form complex networks of interacting nanowires in biofilm, thereby efficiently transferring electrons from distant microbes to the anode<span class="reference"><span class="referencetext"><a target="blank" href="http://www.wiley.com//legacy/wileychi/li1/">Khanal YLaSK. Microbial Fuel Cells, Capter 19. In: Khanal. EbYLaSK, editor. Bioenergy: Principles and Applications. First Edition ed: Published 2017 by John Wiley & Sons, Inc.; 2016.</a></span></span>. | ||
+ | </p> | ||
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<b>Bacterial Nanowires</b><br> | <b>Bacterial Nanowires</b><br> | ||
− | Nanowires are long electrically conductive pili found on the surface of various microorganisms, such as the metal reducing <i>Geobacter sulfurreducens</i>. <i>G. sulfurreducens</i> utilises nanowires to transfer accumulating electrons retrieved from metabolism, to metals in the nearby environment | + | Nanowires are long electrically conductive pili found on the surface of various microorganisms, such as the metal reducing <i>Geobacter sulfurreducens</i>. <span class="highlighted"><i>G. sulfurreducens</i> utilises nanowires to transfer accumulating electrons retrieved from metabolism, to metals in the nearby environment</span><span class="reference"><span class="referencetext"><a target="blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1392927/"> Mahadevan R, Bond DR, Butler JE, Esteve-Nuñez A, Coppi MV, Palsson BO, et al. Characterization of Metabolism in the Fe(III)-Reducing Organism Geobacter sulfurreducens by Constraint-Based Modeling. Applied and Environmental Microbiology. 2006;72(2):1558-68.</a></span></span>. This Gram-negative bacteria is strictly anaerobic, as it is unable to transfer its electrons to the environment in the presence of the highly reducing oxygen. Nanowires found in <i>G. sulfurreducens</i> are type IV pili polymer chains composed of pilA monomers, and they can reach a length of nearly 10 mm<span class="reference"><span class="referencetext"><a target="blank" href="http://jb.asm.org/content/194/10/2551.full"> Richter LV, Sandler SJ, Weis RM. Two Isoforms of Geobacter sulfurreducens pilA Have Distinct Roles in Pilus Biogenesis, Cytochrome Localization, Extracellular Electron Transfer, and Biofilm Formation. Journal of Bacteriology. 2012;194(10):2551-63.</a></span></span>. The proteins required for the effective transfer of electrons by nanowires is a complex and poorly understood system, which includes an extensive series of c-type cytochromes as shown in Figure 14<span class="reference"><span class="referencetext"><a target="blank" href="http://www.biochemsoctrans.org/content/40/6/1295"> Morgado L, Fernandes AP, Dantas JM, Silva MA, Salgueiro CA. On the road to improve the bioremediation and electricity-harvesting skills of Geobacter sulfurreducens: functional and structural characterization of multihaem cytochromes. Biochemical Society transactions. 2012;40(6):1295-301.</a></span></span>.</p> |
− | < | + | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/1/15/T--SDU-Denmark--nanowires.svg" type="image/svg+xml" style="width:80%;"></object></div> |
− | + | <div class="figure-text"><p><b>Figure 14.</b> The electrons from NADH are transferred to menaquinone (MQ), reducing it to menaquinol (MQH<sub>2</sub>), the inner membrane-associated MaCA cytochrome receives the electrons and reduces the periplasmic triheme cytochromes (PpcA-PpcE). The electrons are mediated to the outer membrane-associated cytochromes, OmcB and OmcE, and further transferred to cytochromes on the pili <span class="reference"><span class="referencetext"><a target="blank" href="http://www.biochemsoctrans.org/content/40/6/1295"> Morgado L, Fernandes AP, Dantas JM, Silva MA, Salgueiro CA. On the road to improve the bioremediation and electricity-harvesting skills of Geobacter sulfurreducens: functional and structural characterization of multihaem cytochromes. Biochemical Society transactions. 2012;40(6):1295-301.</a></span></span>. | |
− | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/1/15/T--SDU-Denmark--nanowires.svg" type="image/svg+xml" style="width: | + | </p></div> |
− | + | <p><span class="highlighted">The electrical conductivity of the nanowires in <i>G. sulfurreducens</i> can be optimised by exchanging endogenous <i>pilA</i> with heterologous <i>pilA</i></span> rich in aromatic amino acids. Tan Yang et. al 2017<span class="reference"><span class="referencetext"><a target="blank" href="http://mbio.asm.org/content/8/1/e02203-16.full"> Tan Y, Adhikari RY, Malvankar NS, Ward JE, Woodard TL, Nevin KP, et al. Expressing the Geobacter metallireducens pilA in Geobacter sulfurreducens Yields Pili with Exceptional Conductivity. mBio. 2017;8(1).</a></span></span><span class="highlighted">heterogeneously expressed <i>pilA</i> from <i>G. metallireducens</i> in <i>G. sulfurreducens</i>, which increased the electrical conductivity of the recombinant bacteria 5000-fold</span>. This optimisation holds great potential in the development of highly efficient bacterial strains for MFCs. With the intention of optimising an MFC, <i>G. sulfurreducens</i> is a lot easier to work with than <i>G. metallireducens</i><span class="reference"><span class="referencetext"><a target="blank" href="http://mbio.asm.org/content/8/1/e02203-16.full"> Tan Y, Adhikari RY, Malvankar NS, Ward JE, Woodard TL, Nevin KP, et al. Expressing the Geobacter metallireducens pilA in Geobacter sulfurreducens Yields Pili with Exceptional Conductivity. mBio. 2017;8(1).</a></span></span>, since <i>G. metallireducens</i> has a longer generation time. | |
− | < | + | </p> |
− | <p>The electrical conductivity of the nanowires in <i>G. sulfurreducens</i> can be optimised by exchanging endogenous pilA with heterologous pilA rich in aromatic amino acids. Tan Yang et. al | + | <br> |
− | </p><br> | + | |
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− | + | <p class="P-Larger"><b>Approach</b></p> | |
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− | < | + | <p style="width:100%;"> |
− | <br> | + | <span class="highlighted">Originally, it was intended to implement bacterial nanowires from <i>G. sulfurreducens</i> into <i>E. coli</i></span>. Through research, it was found that the <a href="https://2013.igem.org/Team:Bielefeld-Germany" target="_blank">Bielefeld iGEM team from 2013</a> had come to the conclusion, that <span class="highlighted">this task was too comprehensive to undertake in the limited time of an iGEM project</span>. However, a different approach was deviced, as postdoc Oona Snoeyenbos-West suggested us to use <i>G. sulfurreducens</i> as the model organism for our MFC. |
− | + | <br> | |
+ | <span class="highlighted">It was then decided to work on optimisation of the <i>G. sulfurreducens</i> by increasing the electrical conductivity of its endogenous nanowires. To achieve this, synthesis of the <i>pilA</i> genes from <i>G. metallireducens</i></span> was ordered, which was used to create a BioBrick. Using the same approach for homologous recombination as in the dormancy system, a DNA fragment containing the chloramphenicol resistance cassette of the pSB1C3 backbone, was made for later selection of recombinant <i>G. sulfurreducens</i>. The PCR product was ligated with fragments retrieved from the 500 bp upstream and downstream regions of the chromosomal <i>pilA</i> genes of the <i>G. sulfurreducens</i> PCA strain, creating the fragment seen in Figure 15. | ||
</p> | </p> | ||
+ | <div style="text-align:center;"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/8/85/T--SDU-Denmark--linear-dna-pila-gene.svg" type="image/svg+xml" style="width:80%;"></object></div> | ||
+ | <div class="figure-text"><p><b>Figure 15.</b> The linear DNA fragment intended for homologous recombination into <i>G. sulfurreducens</i>. | ||
+ | </p></div> | ||
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+ | <div style="text-align:center;"><p style="font-size:14px;"><i><a href="#project-results-extracellular-electron-transfer">Click here if you wish to go directly to the Project Demonstration & Results section of the Extracellular Electron Transfer.</a></i></p></div><br> | ||
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− | <div class="svg-project">< | + | <div class="svg-project"><a href="#project-results-extracellular-electron-transfer"><img class="highlighted-image project-overview-icon" src="https://static.igem.org/mediawiki/2017/3/30/T--SDU-Denmark--extracellular-electron-transfer-icon.png" style="width:95%;"></a></div><br> |
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+ | <div class"row"><div class="project-design-headline"><object class="highlighted-image project-design-icon" data="https://static.igem.org/mediawiki/2017/7/7c/T--SDU-Denmark--zzz-icon.svg" type="image/svg+xml"></object><h2>Dormancy System</h2></div></div> | ||
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+ | <div style="text-align:center;"><p><span class="reference-2">Project Overview<span class="referencetext-2"><object data="https://static.igem.org/mediawiki/2017/2/24/T--SDU-Denmark--project-overview-dormancy.svg" style="width:100%;" type="image/svg+xml"></object></span></span></p></div><br> | ||
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+ | <p class="P-Larger"><b>hi hi there</b></p><br> | ||
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+ | <div style="text-align:center;"><p style="font-size:14px;"><i><a href="#demonstration-and-results">Click here to return to the Project Demonstration & Results overview.</a></i></p></div> | ||
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+ | <div class="row margin-bottom-75 padding-top-125" id="project-results-cellulose-breakdown"><div class="col-xs-12"> | ||
+ | <div class="row"><div class="project-design-headline"><object class="highlighted-image project-design-icon" data="https://static.igem.org/mediawiki/2017/f/f8/T--SDU-Denmark--enzyme-icon.svg" type="image/svg+xml"></object><h2>Breakdown of Cellulose</h2></div></div><br> | ||
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+ | <div style="text-align:center;"><p><span class="reference-2">Project Overview<span class="referencetext-2"><object data="https://static.igem.org/mediawiki/2017/0/09/T--SDU-Denmark--project-overview-cellulose-breakdown.svg" style="width:100%;" type="image/svg+xml"></object></span></span></p></div><br> | ||
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+ | <p class="P-Larger"><b><span class="highlighted">hi there</span></b></p> | ||
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+ | <br class="noContent"> | ||
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+ | <div style="text-align:center;"><p style="font-size:14px;"><i><a href="#demonstration-and-results">Click here to return to the Project Demonstration & Results overview.</a></i></p></div> | ||
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+ | <hr> | ||
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+ | <div class="row padding-top-125" id="project-results-extracellular-electron-transfer"><div class="col-xs-12"> | ||
+ | <div class="row"><div class="project-design-headline"><object class="highlighted-image project-design-icon" data="https://static.igem.org/mediawiki/2017/9/9b/T--SDU-Denmark--power-icon.svg" type="image/svg+xml"></object><h2>Extracellular Electron Transfer</h2></div></div><br> | ||
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+ | <div style="text-align:center;"><p><span class="reference-2">Project Overview<span class="referencetext-2"><object data="https://static.igem.org/mediawiki/2017/5/58/T--SDU-Denmark--project-overview-nanowires.svg" style="width:100%;" type="image/svg+xml"></object></span></span></p></div><br> | ||
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+ | </div></div> | ||
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+ | <br class="noContent"> | ||
+ | <div style="text-align:center;"><p style="font-size:14px;"><i><a href="#demonstration-and-results">Click here to return to the Project Demonstration & Results overview.</a></i></p></div> | ||
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− | <p | + | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/8/83/T--SDU-Denmark--SOP-1.pdf" target="_blank"><b>SOP01</b></a> - LA plates with antibiotic</p><br> |
− | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/ | + | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/d/db/T--SDU-Denmark--SOP-2.pdf" target="_blank"><b>SOP02</b></a> - ONC <i>E. Coli</i></p><br> |
− | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/ | + | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/9/9e/T--SDU-Denmark--SOP-3.pdf" target="_blank"><b>SOP03</b></a> - Gel purification</p><br> |
<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/f/f2/T--SDU-Denmark--SOP04.pdf" target="_blank"><b>SOP04</b></a> - Colony PCR with MyTaq</p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/f/f2/T--SDU-Denmark--SOP04.pdf" target="_blank"><b>SOP04</b></a> - Colony PCR with MyTaq</p><br> | ||
<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/1/13/T--SDU-Denmark--SOP05.pdf" target="_blank"><b>SOP05</b></a> - Plasmid MiniPrep</p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/1/13/T--SDU-Denmark--SOP05.pdf" target="_blank"><b>SOP05</b></a> - Plasmid MiniPrep</p><br> | ||
<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/f/f9/T--SDU-Denmark--SOP06.pdf" target="_blank"><b>SOP06</b></a> - TSB transformation</p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/f/f9/T--SDU-Denmark--SOP06.pdf" target="_blank"><b>SOP06</b></a> - TSB transformation</p><br> | ||
<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/5/5f/T--SDU-Denmark--SOP07.pdf" target="_blank"><b>SOP07</b></a> - Fast digest</p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/5/5f/T--SDU-Denmark--SOP07.pdf" target="_blank"><b>SOP07</b></a> - Fast digest</p><br> | ||
− | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/ | + | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/9/97/T--SDU-Denmark--SOP-8.pdf" target="_blank"><b>SOP08</b></a> - M9 minimal medium</p><br> |
<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/4/4e/T--SDU-Denmark--SOP09.pdf" target="_blank"><b>SOP09</b></a> - Ligation</p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/4/4e/T--SDU-Denmark--SOP09.pdf" target="_blank"><b>SOP09</b></a> - Ligation</p><br> | ||
<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/f/fa/T--SDU-Denmark--SOP10.pdf" target="_blank"><b>SOP10</b></a> - Phusion PCR</p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/f/fa/T--SDU-Denmark--SOP10.pdf" target="_blank"><b>SOP10</b></a> - Phusion PCR</p><br> | ||
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<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/3/3a/T--SDU-Denmark--SOP19.pdf" target="_blank"><b>SOP19</b></a> - Preparing Eurofins sequencing samples</p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/3/3a/T--SDU-Denmark--SOP19.pdf" target="_blank"><b>SOP19</b></a> - Preparing Eurofins sequencing samples</p><br> | ||
<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/d/df/T--SDU-Denmark--SOP20.pdf" target="_blank"><b>SOP20</b></a> - Antibiotic stock production</p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/d/df/T--SDU-Denmark--SOP20.pdf" target="_blank"><b>SOP20</b></a> - Antibiotic stock production</p><br> | ||
− | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/ | + | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/a/ab/T--SDU-Denmark--SOP-21.pdf" target="_blank"><b>SOP21</b></a> - Electroporation</p><br> |
<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/6/63/T--SDU-Denmark--SOP22.pdf" target="_blank"><b>SOP22</b></a> - P1 phage transduction</p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/6/63/T--SDU-Denmark--SOP22.pdf" target="_blank"><b>SOP22</b></a> - P1 phage transduction</p><br> | ||
<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/2/2b/T--SDU-Denmark--SOP23.pdf" target="_blank"><b>SOP23</b></a> - Genome extraction</p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/2/2b/T--SDU-Denmark--SOP23.pdf" target="_blank"><b>SOP23</b></a> - Genome extraction</p><br> | ||
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<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/f/f3/T--SDU-Denmark--Protocol06.pdf" target="_blank"><b> Protocol 6</b></a> - Biobrick assembly - Dormancy System Analysis </p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/f/f3/T--SDU-Denmark--Protocol06.pdf" target="_blank"><b> Protocol 6</b></a> - Biobrick assembly - Dormancy System Analysis </p><br> | ||
<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/f/f1/T--SDU-Denmark--Protocol07.pdf" target="_blank"><b> Protocol 7</b></a> - BioBrick assembly - pOmpR characterisation </p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/f/f1/T--SDU-Denmark--Protocol07.pdf" target="_blank"><b> Protocol 7</b></a> - BioBrick assembly - pOmpR characterisation </p><br> | ||
− | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/ | + | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/6/6b/T--SDU-Denmark--Protocol-8.pdf" target="_blank"><b> Protocol 8</b></a> - Biobrick assembly - Carbon fixation </p><br> |
− | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/ | + | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/a/ae/T--SDU-Denmark--Protocol-9.pdf" target="_blank"><b> Protocol 9</b></a> - Biobrick assembly - Cellulose biosynthesis </p><br> |
− | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/c/ | + | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/c/cc/T--SDU-Denmark--Protocol-10.pdf" target="_blank"><b> Protocol 10</b></a> - Biobrick analysis - Growth experiment</p><br> |
<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/d/d2/T--SDU-Denmark--protocol11.pdf" target="_blank"><b> Protocol 11</b></a> - Biobrick assembly - Cellulose secretion </p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/d/d2/T--SDU-Denmark--protocol11.pdf" target="_blank"><b> Protocol 11</b></a> - Biobrick assembly - Cellulose secretion </p><br> | ||
<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/8/86/T--SDU-Denmark--Protocol12.pdf" target="_blank"><b> Protocol 12</b></a> - Biobrick assembly - Cellulose consumption </p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/8/86/T--SDU-Denmark--Protocol12.pdf" target="_blank"><b> Protocol 12</b></a> - Biobrick assembly - Cellulose consumption </p><br> | ||
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<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/3/30/T--SDU-Denmark--Protocol14.pdf" target="_blank"><b> Protocol 14</b></a> - Cellulose degradation analysis - SDS-page</p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/3/30/T--SDU-Denmark--Protocol14.pdf" target="_blank"><b> Protocol 14</b></a> - Cellulose degradation analysis - SDS-page</p><br> | ||
<p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/5/56/T--SDU-Denmark--Protocol15.pdf" target="_blank"><b> Protocol 15</b></a> - Cellulose degradation - Cellulase screening</p><br> | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/5/56/T--SDU-Denmark--Protocol15.pdf" target="_blank"><b> Protocol 15</b></a> - Cellulose degradation - Cellulase screening</p><br> | ||
+ | <p><a class="modal-link" href="https://static.igem.org/mediawiki/2017/4/4b/T--SDU-Denmark--Protocol16.pdf" target="_blank"><b> Protocol 16</b></a> - Electrical analysis - Conductivity test</p><br> | ||
</div> | </div> | ||
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<p class="raleway citation"><i>“Hauge’s square is a spot in Bolbro, which we aim to make a central place in Bolbro; a place that invites the citizen to meet and dwell. <span class="highlighted">Your solution should be able to contribute to help citizens recharge their phones, e.g. a solution could be implanting the PowerLeaf into a interactive furniture, but where the demand an aesthetic pleasing design still remains.</span>”</i></p> | <p class="raleway citation"><i>“Hauge’s square is a spot in Bolbro, which we aim to make a central place in Bolbro; a place that invites the citizen to meet and dwell. <span class="highlighted">Your solution should be able to contribute to help citizens recharge their phones, e.g. a solution could be implanting the PowerLeaf into a interactive furniture, but where the demand an aesthetic pleasing design still remains.</span>”</i></p> | ||
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− | <div class="integrated-practices-prototypes"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/b/b7/T--SDU-Denmark--bench-human-practices.svg" type="image/svg+xml" style="width:100%;"></object></div> | + | <div class="integrated-practices-prototypes"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/b/b7/T--SDU-Denmark--bench-human-practices.svg" type="image/svg+xml" style="width:100%; border-radius:5px;"></object></div> |
<br> | <br> | ||
− | <p class="raleway citation"><i>“A part of the vision of this project is the concept of making a pop-up park with differently designed multi-furniture, preferably in wood and organic design, which are removable to the various areas where we are going to develop in the district. It is furniture that should be able to be used to relax in and at the same time also motivates children to move. <span class="highlighted">There is also a need for charging devices and it therefore demands that your solution is an integrated</span>, but still mobile solution, as the park will move physically over time.”</i></p> | + | <p class="raleway citation"><i>“A part of the vision of this project is the concept of making a pop-up park with differently designed multi-furniture, preferably in wood and organic design, which are removable to the various areas where we are going to develop in the district. It is furniture that should be able to be used to relax in and at the same time also motivates children to move. <span class="highlighted">There is also a need for charging devices and it therefore demands that your solution is an integrated</span>, but still mobile solution, as the park will move physically over time. Finally, the playground is to be developed especially for the young audience, which is a major consumer of power for phones. <span class="highlighted">The playground must be a place where youngsters hang out after school, while maintaining its status as a green space</span>.”</i></p> |
<br> | <br> | ||
− | <div class="integrated-practices-prototypes"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/f/f9/T--SDU-Denmark--powerleaf-integrated-bench.svg" type="image/svg+xml" style="width:100%; | + | <div class="integrated-practices-prototypes"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/f/f9/T--SDU-Denmark--powerleaf-integrated-bench.svg" type="image/svg+xml" style="width:100%; border-radius:5px;"></object></div> |
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<br> | <br> | ||
<p>The making of the furniture as a prototype called for a revisit of our safety concerns. We now knew that children would be climbing and playing on the furniture, making it crucial that the material of the PowerLeaf will not break. This is a concern we discussed with Flemming Christiansen, which you can read all about next.</p> | <p>The making of the furniture as a prototype called for a revisit of our safety concerns. We now knew that children would be climbing and playing on the furniture, making it crucial that the material of the PowerLeaf will not break. This is a concern we discussed with Flemming Christiansen, which you can read all about next.</p> | ||
− | <br class="noContent"> | + | <div id="plastic-expert" style="margin-top:-70px; padding-top:70px;"><br class="noContent"> |
<br class="noContent"> | <br class="noContent"> | ||
<p class="P-Larger"><b>Finding the Proper Material</b></p> | <p class="P-Larger"><b>Finding the Proper Material</b></p> | ||
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<div><img class="interview-images" src="https://static.igem.org/mediawiki/2017/d/db/T--SDU-Denmark--flemming.jpg"/><p style="display:inline;">For the purpose of finding the necessary materials for our prototype, <span class="highlighted">we contacted one of the leading plastic experts in Denmark, Flemming Christiansen</span> , who acts as the market development manager of SP Moulding. He has been acting as a plastics consultant since his graduation as a master of science in Engineering, with a speciality in plastics. A meeting was quickly arranged for the purpose of confirming our criteria, the technical design, the material, and the possible price of creating the PowerLeaf. </p></div> | <div><img class="interview-images" src="https://static.igem.org/mediawiki/2017/d/db/T--SDU-Denmark--flemming.jpg"/><p style="display:inline;">For the purpose of finding the necessary materials for our prototype, <span class="highlighted">we contacted one of the leading plastic experts in Denmark, Flemming Christiansen</span> , who acts as the market development manager of SP Moulding. He has been acting as a plastics consultant since his graduation as a master of science in Engineering, with a speciality in plastics. A meeting was quickly arranged for the purpose of confirming our criteria, the technical design, the material, and the possible price of creating the PowerLeaf. </p></div> | ||
<br> | <br> | ||
− | <p> | + | <p>In accordance with our established criteria, <span class="highlighted">Mr. Christiansen suggested that we use the plastic known as Polycarbonate, specifically Lexon 103R-III</span> <span class="reference"><span class="referencetext"><a target="blank" href="https://plastics.ulprospector.com/datasheet/e17532/lexan-103r-resin"> Polycarbonate</a></span></span>. Unfortunately, the material cannot fulfil the criteria on its own. He therefore suggested that we take a few liberties with it. In order to prevent UV degradation to the exposed parts, we will be adding certain additives to the surface. This increases the UV resistance of the device, without hindering the sunlight from reaching the bacteria. |
<br> | <br> | ||
During our conversations with Mr. Christiansen, we reached the topic of what to do in case of a breach. Should the container against all expectations be damaged, the environment will be exposed to the GMO inside. The solution we came up with was the possible implementation of a kill-switch in the inner compartment, making it vulnerable to sunlight. Should the bacteria of said unit be exposed to sunlight, they would perish. <span class="highlighted">As the outer compartment would be dependent on the continued coexistence of the two units, the entire GMO system would be purged in case of a breach</span> . To implement this feature, the inner chamber would be covered with Carbon Black, which has the ability to absorb sunlight, thus leaving the compartment itself in darkness. <br> | During our conversations with Mr. Christiansen, we reached the topic of what to do in case of a breach. Should the container against all expectations be damaged, the environment will be exposed to the GMO inside. The solution we came up with was the possible implementation of a kill-switch in the inner compartment, making it vulnerable to sunlight. Should the bacteria of said unit be exposed to sunlight, they would perish. <span class="highlighted">As the outer compartment would be dependent on the continued coexistence of the two units, the entire GMO system would be purged in case of a breach</span> . To implement this feature, the inner chamber would be covered with Carbon Black, which has the ability to absorb sunlight, thus leaving the compartment itself in darkness. <br> | ||
The process of constructing our device would be through an extensive use of Injection Moulding, which is considered pricey equipment. The material is expensive at 4-5.5 USD per kg at orders above 1 metric ton, according to Mr. Christiansen, but its longevity and durability means it would not need to be replaced for a long time. Lastly, we discussed the reusability of Polycarbonate, which he assured us was of no concern, as the material could be <i>reused</i> and <i>recycled</i> with ease. | The process of constructing our device would be through an extensive use of Injection Moulding, which is considered pricey equipment. The material is expensive at 4-5.5 USD per kg at orders above 1 metric ton, according to Mr. Christiansen, but its longevity and durability means it would not need to be replaced for a long time. Lastly, we discussed the reusability of Polycarbonate, which he assured us was of no concern, as the material could be <i>reused</i> and <i>recycled</i> with ease. | ||
</p><br> | </p><br> | ||
− | <div class="integrated-practices-prototypes"><object class="highlighted-image" data="https://static.igem.org/mediawiki/2017/ | + | <div class="integrated-practices-prototypes"><object class="highlighted-image" style="width:100%; border-radius:5px;" data="https://static.igem.org/mediawiki/2017/7/76/T--SDU-Denmark--leaf-prototype.svg" type="image/svg+xml"></object></div><br> |
+ | <p>hejmeddig</p> | ||
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− | <h2><span class="highlighted">Education & Public Engagement</span></h2><br><h4>- <i>A | + | <h2><span class="highlighted">Education & Public Engagement</span></h2><br><h4>- <i>A Trip to the Future and Beyond!</i></h4><hr> |
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+ | <div class="row"><div class="col-xs-12"><div style="text-align:center;"><object class="highlighted-image" style="width:100%; border-radius:5px;" data="https://static.igem.org/mediawiki/2017/4/47/T--SDU-Denmark--future-generations.svg" type="image/svg+xml"></object></div></div></div><br> | ||
+ | |||
+ | <p><i>If you want change, look to the future!</i> Such was the wording of our core philosophy. A philosophy that was carried out, by <span class="highlighted">reaching out to the people of our society to ensure the engagement of the next generation, within the world of synthetic biology.</span> | ||
+ | <br> | ||
+ | Ever since World War II, the West has seen an expansion and intensification of anti-scientific sentiment, which today primarily concern Genetically Modified Organisms (GMO). We will for that reason explore GMO’s role in history, to see if a historical perspective will allow us reach a new understanding of these sentiments. You can read all about it <span class="btn-link btn-lg" data-toggle="modal" data-target="#historical-perspective">here</span>.</p><br> | ||
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+ | <div class="modal fade" id="historical-perspective" tabindex="-1" data-backdrop="false" style="background-color:rgba(0,0,0,0.6);"> | ||
+ | <div class="modal-dialog modal-lg"> | ||
+ | <div class="modal-content"> | ||
+ | <div class="modal-header"> | ||
+ | <button type="button" class="close" data-dismiss="modal">×</button> | ||
+ | <h2 class="modal-title">A Historical Perspective on GMO</h2> | ||
+ | </div> | ||
+ | <div class="modal-body" margin-right="10%"> | ||
+ | <div class="row"> | ||
+ | <div class="col-md-1"></div> | ||
+ | <div class="col-md-10"> | ||
+ | <p class="P-Larger"><b>From Food Concerns to Sustainable Energy</b></p><br> | ||
+ | <p>When talking about the history of GMO, we have the rare privilege of choice, as depending on how you define GMO, One could potentially choose any historical period as their starting point. For instance, we could be examining the breeding of wolves to dogs, or simple agriculture, where the bad seeds are destroyed in favour of higher quality crops<span class="reference"><span class="referencetext"><a target="blank" href=" http://sitn.hms.harvard.edu/flash/2015/from-corgis-to-corn-a-brief-look-at-the-long-history-of-gmo-technology/">Rangel G. From Corgis to Corn: A Brief Look at the Long History of GMO Technology. Genetically Modified Organisms and Our Food. August 2015.</a></span></span> | ||
+ | <br> | ||
+ | For the purpose of narrative, we will be starting our examination with the dawn of the 20<sup>th</sup> century. A time in which stale and rotten food lead to health concerns. Through several years, the public was continuously made aware of health problems regarding food in the United States. This culminated in the 1906 statute:, which allowed the inspection and ban of products<span class="reference"><span class="referencetext"><a target="blank"href="https://www.revolvy.com/main/index.php?s=Federal%20Food%20and%20Drugs%20Act%20of%201906&item_type=topic"> JP S. The 1906 Food and Drugs Act and Its Enforcement. FDA History - Part I US Food and Drug Administration. 2013.</a></span></span>. During the time leading up to this act, the public grew to appreciate items labeled as pure. A trend we can observe in most journalistic material from the time period<span class="reference"><span class="referencetext"><a target="blank" href="http://chroniclingamerica.loc.gov/lccn/2010270501/"> O’Keefe TJ. The Alliance herald. : (Alliance, Box Butte County, Neb.) 1902-1922. T.J. O'Keefe; 1902.</a></span></span> | ||
+ | <br> | ||
+ | This need for pure food naturally originated partly from several years of unsatisfactory food and health concerns<span class="reference"><span class="referencetext"><a target="blank" href="https://www.revolvy.com/main/index.php?s=Federal%20Food%20and%20Drugs%20Act%20of%201906&item_type=topic"> JP S. The 1906 Food and Drugs Act and Its Enforcement. FDA History - Part I US Food and Drug Administration. 2013.</a></span></span>, and partly from a political fiction: The Jungle, by Upton Sinclair<span class="reference"><span class="referencetext"><a target="blank" href="https://www.abebooks.com/Jungle-Sinclair-Upton-Grosset-Dunlap-New/1291165375/bd"> Sinclair U. The Jungle. New York: Grosset & Dunlap,; 1906 1906.</a></span></span>. | ||
+ | The readers became aware of unsanitary practices in the American food industry. Sinclair was considered a whistleblower, having exposed the practices of the food industry. After the act of 1906, we can observe a rise in concerns over the purity of food, which in turn lead to a focus on maintaining a certain standard in foods. Over time, this concern became the driving force behind the development of pesticides, and to a certain extent, GMO. With the introduction of these solutions to food purity, a new and opposite response could quickly be observed in the public. With pesticides and GMO, the public quickly grew concerned that food would be unnatural, and thus we can observe what is known as a reverse halo effect<span class="reference"><span class="referencetext"><a target="blank" href="https://www.newyorker.com/tech/elements/the-psychology-of-distrusting-g-m-o-s"> Konnikova M. The Psychology of Distrusting G.M.O.s. THE NEW YORKER. 2013.</a></span></span>. A reverse halo effect is defined by the unconscious creation of a negative assumption based on a positive evaluation. In this case, the positive evaluation, would be the ensured purity and health benefits of GMO foods, where the negative assumption would be the concerns for <i>unnaturalness</i>.<br> | ||
+ | So we detect a tendency in the public to follow a reverse halo effect, which is most often associated with GMO foods. The problem we face today, is the continuation of this reverse halo effect, where the public would receive any GMO device negatively, simply by association to the word GMO. So how do we change this dynamic between GMO and the public?<br> | ||
+ | The conclusion we reached was that in order to change a tendency in public opinion, it was important to educate the coming generations on the possibilities of GMO. Another important aspect seemed to be a general perception of GMO as an unnatural element that would harm both humans and nature alike. As such, we wanted to illustrate how GMO could be used, not to harm nature, but to help lead it towards a more sustainable future. So, we set out to teach children of all ages about GMO in general, as well as about our own PowerLeaf, to show them that this concept, which is considered to be unnatural, could actually be used to help nature. | ||
+ | </p> | ||
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+ | <div class="modal-footer"> | ||
+ | <a href="" class="btn btn-default" data-dismiss="modal">Close</a> | ||
+ | </div> | ||
+ | </div> | ||
+ | </div> | ||
+ | </div> | ||
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<p><span class="highlighted">At the Danish Science Festival we hosted a workshop for kindergarteners</span>, during which we taught them about <span class="highlighted">synthetic biology, sustainability, the history of GMO, and bioethics.</span> The children would in turn teach us as well, as they showed us the endless possibilities for bacteria designs, through <span class="highlighted">the “Draw-a-Bacteria”-contest.</span> This <a href="#inspiration-from-children" target="_blank">inspired</a> us to reevaluate our initial idea.</p><br> | <p><span class="highlighted">At the Danish Science Festival we hosted a workshop for kindergarteners</span>, during which we taught them about <span class="highlighted">synthetic biology, sustainability, the history of GMO, and bioethics.</span> The children would in turn teach us as well, as they showed us the endless possibilities for bacteria designs, through <span class="highlighted">the “Draw-a-Bacteria”-contest.</span> This <a href="#inspiration-from-children" target="_blank">inspired</a> us to reevaluate our initial idea.</p><br> | ||
− | <img /> | + | <div class="row"> |
+ | <div class="col-sm-6 verticalAlignColumnsAbstract"><div style="text-align:center; margin-top:20px;"><img class="education-images" src="https://static.igem.org/mediawiki/2017/2/24/T--SDU-Denmark--science-festival-picture.jpg" style="width:90%;"/></div></div> | ||
+ | |||
+ | <div class="col-sm-6 verticalAlignColumnsAbstract"><div style="text-align:center; margin-top:20px;"><img class="education-images" src="https://static.igem.org/mediawiki/2017/c/c7/T--SDU-Denmark--magnus-picture.jpg" style="width:90%;"/></div></div> | ||
+ | </div> | ||
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+ | <br class="noContent"> | ||
+ | <br class="noContent"> | ||
<p class="P-Larger"><b><span class=”highlighted”>School Project Interview with 6<sup>th</sup> Graders</b></span></p><br class=”miniBreak”> | <p class="P-Larger"><b><span class=”highlighted”>School Project Interview with 6<sup>th</sup> Graders</b></span></p><br class=”miniBreak”> | ||
<p>Following the Danish Science Festival, we were contacted by two enthusiastic 6<sup>th</sup> graders, Bastian and Magnus. The two boys wanted to learn more about iGEM and GMO, which they intended to write about in a school project. They were curious to what range GMO could be used, and how we utilised it in our project, the PowerLeaf.</p><br> | <p>Following the Danish Science Festival, we were contacted by two enthusiastic 6<sup>th</sup> graders, Bastian and Magnus. The two boys wanted to learn more about iGEM and GMO, which they intended to write about in a school project. They were curious to what range GMO could be used, and how we utilised it in our project, the PowerLeaf.</p><br> | ||
− | < | + | <br class="noContent"> |
− | + | <br class="noContent"> | |
<p class="P-Larger"><b><span class=”highlighted”>UNF Summer Camp</b></span></p><br class=”miniBreak”> | <p class="P-Larger"><b><span class=”highlighted”>UNF Summer Camp</b></span></p><br class=”miniBreak”> | ||
− | <p>The UNF Summer Camp is an opportunity for high school students to show extra dedication towards science. We talked to some of the brightest young minds imaginable, all of whom aim to work in different fields of science in the future. <span class="highlighted">At the summer camp, we held a presentation about our project, the iGEM competition, as well as how to handle and work with genes. | + | <p>The UNF Summer Camp is an opportunity for high school students to show extra dedication towards science. We talked to some of the brightest young minds imaginable, all of whom aim to work in different fields of science in the future. <span class="highlighted">At the summer camp, we held a presentation about our project, the iGEM competition, as well as how to handle and work with genes. We taught them how to assemble BioBricks and provided them with BioBricks for DNA assembly experiments, creating a ‘hands-on’ experience for these enthusiastic teenagers.</span> |
− | We taught them how to assemble BioBricks and provided them with BioBricks for DNA assembly experiments, creating a ‘hands-on’ experience for these enthusiastic teenagers.</span> | + | |
<br> | <br> | ||
− | One of the high school students suggested that the Powerleaf should be able to rotate according to the sun, to ensure maximum exposure and outcome. We took this brilliant advice into consideration and contacted Robot Systems Engineer student, Oliver Klinggaard, who helped us with the potential implementation of a pan/tilt system. He provided us with his recent project report on the subject, as well as a description of the adjustments required for the implementation in our system, which you can find | + | One of the high school students suggested that the Powerleaf should be able to rotate according to the sun, to ensure maximum exposure and outcome. We took this brilliant advice into consideration and contacted Robot Systems Engineer student, Oliver Klinggaard, who helped us with the potential implementation of a pan/tilt system. He provided us with his recent project report on the subject, as well as a description of the adjustments required for the implementation in our system, which you can find <a href="https://static.igem.org/mediawiki/2017/9/99/T--SDU-Denmark--PanTilt-system.pdf" target="_blank">here</a>. |
<br> | <br> | ||
Two students from the UNF Summer Camp thought the PowerLeaf was an interesting approach to sustainable energy, and they wanted to hear even more! So, they contacted us in late October, as they were interested to work on a project about green technology.</p><br> | Two students from the UNF Summer Camp thought the PowerLeaf was an interesting approach to sustainable energy, and they wanted to hear even more! So, they contacted us in late October, as they were interested to work on a project about green technology.</p><br> | ||
− | < | + | <div style="text-align:center;"><img class="education-images" src="https://static.igem.org/mediawiki/2017/7/77/T--SDU-Denmark--unf-picture.jpg" style="width:70%"/></div><br> |
+ | |||
+ | <br class="noContent"> | ||
+ | <br class="noContent"> | ||
<p class="P-Larger"><b><span class=”highlighted”>The Academy for Talented Youth</b></span></p><br class=”miniBreak”> | <p class="P-Larger"><b><span class=”highlighted”>The Academy for Talented Youth</b></span></p><br class=”miniBreak”> | ||
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+ | <br class="noContent"> | ||
+ | <br class="noContent"> | ||
<p class="P-Larger"><b><span class=”highlighted”>Presentations for the Local Schools</b></span></p><br class=”miniBreak”> | <p class="P-Larger"><b><span class=”highlighted”>Presentations for the Local Schools</b></span></p><br class=”miniBreak”> | ||
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<span class="highlighted">An 8<sup>th</sup> grade class from the local public school, Odense Friskole, were invited to see our laboratory workspace.</span> It was a challenge to successfully convey our project and the concept of synthetic biology in a way that would be easily understandable by 8<sup>th</sup> graders, who have only recently been introduced to science. A challenge that we accepted and solved, by relaying the fundamentals in synthetic biology, e.g. the basics of a cell, DNA, and GMO. | <span class="highlighted">An 8<sup>th</sup> grade class from the local public school, Odense Friskole, were invited to see our laboratory workspace.</span> It was a challenge to successfully convey our project and the concept of synthetic biology in a way that would be easily understandable by 8<sup>th</sup> graders, who have only recently been introduced to science. A challenge that we accepted and solved, by relaying the fundamentals in synthetic biology, e.g. the basics of a cell, DNA, and GMO. | ||
<br> | <br> | ||
− | <span class="highlighted">From all of these presentations and interactions with younger individuals, we had a strong intuition that it had made an influence on their awareness of synthetic biology. This intuition was supported by the positive feedback provided by teachers and students.</span> An awareness of how new scientific technologies can be a feasible solution to a possible energy crisis. Technologies such as synthetic biology, with endless capabilities to achieve efficacy, since no one knows what tomorrow brings. For more information about this read <a | + | <span class="highlighted">From all of these presentations and interactions with younger individuals, we had a strong intuition that it had made an influence on their awareness of synthetic biology. This intuition was supported by the positive feedback provided by teachers and students.</span> An awareness of how new scientific technologies can be a feasible solution to a possible energy crisis. Technologies such as synthetic biology, with endless capabilities to achieve efficacy, since no one knows what tomorrow brings. For more information about this read <a href="#future-igem-teams" target="_blank">To Future iGEM Teams</a></p><br> |
+ | <br class="noContent"> | ||
<p class="P-Larger"><b><span class=”highlighted”>Final Presentation at SDU-Denmark</b></span></p><br class=”miniBreak”> | <p class="P-Larger"><b><span class=”highlighted”>Final Presentation at SDU-Denmark</b></span></p><br class=”miniBreak”> | ||
<p><span class="highlighted">The day before we travelled to Boston, we booked one of the big auditoriums at the University of Southern Denmark, for the final rehearsal of our jamboree presentation.</span> We made sure to take note of all the feedback and tips we received, while also implementing these into our final presentation. This event was promoted on all the information screens at our university in order to attract a broad audience and increase the interest for iGEM. Thus, making it possible to reach a substantial amount of future applications for the SDU-iGEM team and <span class="highlighted">ensure that the iGEM spirit will continue to prosper in the future!</span> </p><br> | <p><span class="highlighted">The day before we travelled to Boston, we booked one of the big auditoriums at the University of Southern Denmark, for the final rehearsal of our jamboree presentation.</span> We made sure to take note of all the feedback and tips we received, while also implementing these into our final presentation. This event was promoted on all the information screens at our university in order to attract a broad audience and increase the interest for iGEM. Thus, making it possible to reach a substantial amount of future applications for the SDU-iGEM team and <span class="highlighted">ensure that the iGEM spirit will continue to prosper in the future!</span> </p><br> | ||
+ | <br class="noContent"> | ||
<p class="P-Larger"><b><span class=”highlighted”>Social Media</b></span></p><br class=”miniBreak”> | <p class="P-Larger"><b><span class=”highlighted”>Social Media</b></span></p><br class=”miniBreak”> | ||
<p>Social media is an easy way to impact a high number of people, so a strategy was concocted with the intention of reaching as many people as possible with our outreach. | <p>Social media is an easy way to impact a high number of people, so a strategy was concocted with the intention of reaching as many people as possible with our outreach. | ||
<span class="highlighted">Our strategy yielded marvellous results, amongst which was a video on our project, that reached viewers equal to 16% of our hometown’s population, along with becoming the second most seen bulletin of the year from University of Southern Denmark.</span> They have also asked us to film our experiences at the Jamboree, which will feature on the homepage of the student’ initiative BetonTV. | <span class="highlighted">Our strategy yielded marvellous results, amongst which was a video on our project, that reached viewers equal to 16% of our hometown’s population, along with becoming the second most seen bulletin of the year from University of Southern Denmark.</span> They have also asked us to film our experiences at the Jamboree, which will feature on the homepage of the student’ initiative BetonTV. | ||
− | <span class="highlighted">Several articles were written about our project in local newspapers, one was even featured in the saturday special.</span><span class="btn-link btn-lg" data-toggle="modal" data-target="#about-social-media"> | + | <span class="highlighted">Several articles were written about our project in local newspapers, one was even featured in the saturday special.<br>You can read all about our social media strategy and results </span><span class="btn-link btn-lg" data-toggle="modal" data-target="#about-social-media">here</span>. The commercial can be seen right here:</p><br> |
+ | |||
+ | |||
+ | <!-- MP4 fra iGEM serverne --> | ||
+ | <div style='position: relative; width: 100%; height: 0px; padding-bottom: 60%;'> | ||
+ | <video controls class="video-js vjs-default-skin vjs-big-play-centered" style='position: absolute; left: 0px; top: 0px; width: 100%; height: 100%'> | ||
+ | <source src="https://static.igem.org/mediawiki/2017/7/7a/T--SDU-Denmark--Commercial-vid.mp4" type="video/mp4"> | ||
+ | </video> | ||
+ | </div> | ||
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+ | <!--Start of modal Social Media--> | ||
+ | <div class="modal fade" id="about-social-media" tabindex="-1" data-backdrop="false" style="background-color:rgba(0,0,0,0.6);"> | ||
+ | <div class="modal-dialog modal-lg"> | ||
+ | <div class="modal-content"> | ||
+ | <div class="modal-header"> | ||
+ | <button type="button" class="close" data-dismiss="modal">×</button> | ||
+ | <h2 class="modal-title">Social Media Report</h2> | ||
+ | </div> | ||
+ | <div class="modal-body" margin-right="10%"> | ||
+ | <div class="row"> | ||
+ | <div class="col-md-1"></div> | ||
+ | <div class="col-md-10"> | ||
+ | |||
+ | |||
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+ | <div style="text-align:center;"><p class="raleway P-Larger"><i>"I hate social media. I have Twitter, just so I can tell people what to buy.”</i></p><br><p class="raleway"><i>Louis C. K. </i></p></div><br><br class="noContent"> | ||
+ | <br> | ||
+ | <p class="P-Larger"><b>Introduction</b></p><br class="miniBreak"> | ||
+ | <p> | ||
+ | As part of our iGEM project we wanted to raise awareness on synthetic biology. As such it seemed beneficial to have a successful social media strategy. The motivation for such a strategy came from the knowledge that social media in general has a large influence on people, especially the younger generation. | ||
+ | <span class="reference"><span class="referencetext"><a target="blank" href="http://www.emeraldinsight.com/doi/abs/10.1108/02634500810902839">Opportunities for green marketing: young | ||
+ | consumers</a></span></span>. | ||
+ | <span class="reference"><span class="referencetext"><a target="blank" href="http://www.businessnewsdaily.com/4373-young-better-earth-day-targets.html">Social Media Influencing Green | ||
+ | Buying</a></span></span> | ||
+ | </p> | ||
+ | <p class="P-Larger"><b> Our Strategy</b></p> | ||
+ | <br> | ||
+ | <p> | ||
+ | The design of our logo consisting of a light font and a picture of a leaf combined with an electrical plug, was determined in the start of April. We sought to make a simple logo that showed the essence of our project, The PowerLeaf, not only in name but in brand as well. | ||
+ | <br> | ||
+ | During spring we narrowed down the relevant hashtags of our Twitter and Instagram to #science, #igem, #sdu, #gmo, and #forsksdu. These hashtags were used at relevant occasions and generally helped expanding our reach on social media. A few times we even used a couple of silly hashtags like #adventuretime and #lifechoices when we found it appropriate. | ||
+ | <br> | ||
+ | A complete relaunch of our social media platforms was made in the start of April. One of the changes we made was the setup of the Facebook page and Twitter account, that we changed to resemble an enterprise. | ||
+ | </p> <br> | ||
+ | <p class="P-Larger"><b> Results</b></p> | ||
+ | <div class="row"> | ||
+ | <div class="col-md-6"> | ||
+ | <p> Looking at Figure 1 we see the number of followers on our Facebook page throughout the year. There is a sharp increase around the start of April, this correlate nicely with the relaunch of our social media. Since we started using the Facebook page on March 1<sup>st</sup>, we have seen an increase of followers on 44%. | ||
+ | <br> | ||
+ | Figure 2 shows the number of unique interactions with our Facebook posts each day. Some posts gained around 200 interactions per day, while the highest amount of interactions per day was seen at end of April. This high amount of interactions correlates with us being at the Danish Science Festival, where we inoculated bacteria from the fingers of the attendants on agar plates. The photo gallery of these plates was widely shared on our Facebook page, and it probably was the reason for the rise in amounts of interactions. | ||
+ | <br> | ||
+ | During the summer, we realised that an increasing fraction of our followers on Facebook were non-Danish speakers. Therefore, we set out to analyse the distribution of first languages among our followers seen in Figure 3, which showed that one in three of our followers were not speaking Danish as their first language. This data led to us switching the language used in our Facebook posts from Danish to English. </p></div> | ||
+ | <div class="col-md-6"> | ||
+ | <div style="text-align:center;"><object data="https://static.igem.org/mediawiki/2017/0/08/SDU-Denmark-SoMe-Followers-Fig.svg" type="image/svg+xml" style="width:100%;"></object></div> | ||
+ | <br> | ||
+ | <div class="figure-text"><p><b>Figure 1.</b> Number of followers on our Facebook page throughout the year.</p></div> | ||
+ | <br class="noContent"> | ||
+ | |||
+ | <div style="text-align:center;"><object data="https://static.igem.org/mediawiki/2017/8/87/T--SDU-Denmark--SoMe-Interaction-Fig.svg" type="image/svg+xml" style="width:100%;"></object></div> | ||
+ | <br> | ||
+ | <div class="figure-text"><p><b>Figure 2. </b> Unique interactions per day on our Facebook page. </p></div> | ||
+ | <br class="noContent"> | ||
+ | <div style="text-align:center;"><object data="https://static.igem.org/mediawiki/2017/0/06/T--SDU-Denmark--SoMe-Language-Fig.svg" type="image/svg+xml" style="width:100%;"></object></div> | ||
+ | <br> | ||
+ | <div class="figure-text"><p><b>Figure 3.</b> Distribution of first language among our followers</p></div> | ||
+ | <br class="noContent"> | ||
+ | </div> | ||
+ | </div> | ||
+ | <p>On the 8<sup>th</sup> of September a commercial about our project aired on the website and Facebook page of the University of Southern Denmark. We made this commercial in collaboration with the communications department of the University of Southern Denmark, specifically a producer named Anders Boe. It was seen 27,526 times, which is equivalent to 16% of our hometowns population. The click-through rate was around 10%, which is much greater than the average rate of videos on their Facebook page. The commercial led to random people, including doctors on the hospital of Odense, asking team members about the project and about GMO in general. With all this in mind it seems fair to state that the commercial was a smash hit of our human outreach and our engagement in the social media. In combination with our easily recognisable logo and our human outreach initiatives, we have been using our social media as a platform to show interest in synthetic biology and for sharing our work. | ||
+ | <br> | ||
+ | After seeing the commercial a local newspaper reached out to us to bring an interview in their Saturday special <span class="reference"><span class="referencetext"><a target="blank" href="https://www.fyens.dk/indland/Forsoemt-sommer-Studerende-bruger-ferien-paa-solceller-af-bakterier/artikel/3180933">Newspaper article from Fyens.dk (Danish)</a></span></span>. In collaboration with the student media RUST and Beton TV we have been featured in their magazine and a video of our attendance in Boston will be shown on their Facebook page briefly after our return. This is done to ensure an awareness of the iGEM competition among the students on the University of Southern Denmark. We hope this will inspire a lot of students to apply for the iGEM team next year, since it is a hallmark of the SDU-Denmark team to be interdisciplinary. | ||
+ | <br> | ||
+ | The effort put into our social media strategy and our goal of following it has paid off. Social media has shaped our outreach and made it possible for us to talk about iGEM and our project to people we did not know. Several times our outreach has led us to public discussion of GMO and solar panels due to persons contacting us, wanting to know more. | ||
+ | </p> | ||
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+ | <div class="col-md-1"></div> | ||
+ | </div> | ||
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+ | <div class="modal-footer"> | ||
+ | <a href="" class="btn btn-default" data-dismiss="modal">Close</a> | ||
+ | </div> | ||
+ | </div> | ||
+ | </div> | ||
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+ | <!--End of modal Social media report--> | ||
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This is also a very crucial part of the PowerLeaf, since it would otherwise be generating an electrical current non-stop, even when not needed. Thereby overthrowing the potential for long term-storage of solar energy. We believe this can be solved either through precise gene circuit regulation or by physical compartmentalisation, but there might be even more elegant ways in which to handle this challenge.</li><br class="noContent"> | This is also a very crucial part of the PowerLeaf, since it would otherwise be generating an electrical current non-stop, even when not needed. Thereby overthrowing the potential for long term-storage of solar energy. We believe this can be solved either through precise gene circuit regulation or by physical compartmentalisation, but there might be even more elegant ways in which to handle this challenge.</li><br class="noContent"> | ||
<li><span class="highlighted"><b>Physical Engineering of the Hardware</b></span><br class="miniBreak"> | <li><span class="highlighted"><b>Physical Engineering of the Hardware</b></span><br class="miniBreak"> | ||
− | It should be possible for the energy storing unit to convert CO<sub>2</sub> into cellulose, thereby producing O<sub>2</sub> making its chamber aerobic. For the energy converting unit to effectively transfer retrieved electrons to an anode, it requires anaerobic conditions. Thus the removal of O<sub>2</sub> from the device is an obstacle to overcome. It will require some out-of-the-box thinking to come up with a novel idea without having to require more energy than produced.</li><br> | + | It should be possible for the energy storing unit to convert CO<sub>2</sub> into cellulose, thereby producing O<sub>2</sub> making its chamber aerobic. For the energy converting unit to effectively transfer retrieved electrons to an anode, it requires anaerobic conditions. Thus the removal of O<sub>2</sub> from the device is an obstacle to overcome. It will require some out-of-the-box thinking to come up with a novel idea without having to require more energy than produced.<br>To make a workable prototype of the PowerLeaf, proper engineering of the hardware is necessary. This includes elements such as anodes, chambers, circulation of important nutrients, removal of wastes, and the use of appropriate materials. We worked out the optimal type of plastic for the system with the help of a local expert. You can read about our work regarding the plastic <a href="#plastic-expert" target="_blank">here</a>.</li><br> |
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Revision as of 22:20, 1 November 2017