Our goal is to design and build a cation responsive strain of E. coli to sense and respond to increases in ionic strength of its environment. Recently, it has been reported that cells in biofilms exhibit long distance intercellular communication using ion gradients that affect substrate utilization (biofilm feeding). We believe this phenomenon could be important in pathogenicity of environmental toxicants when they interact with biofilm microbiomes of the human body, which are often the first line of defense for exposure. Additionally, intercellular communication, between microbial cells of a biofilm or between microbial cells and host cells, could be beneficial for drug delivery and efficacy of therapeutics. Both toxicants and therapeutics are known to affect the ionic environment of the mucosal lining of the human body. If an organism were engineered to respond to an ionic change, a protective (in the case of toxicant) or beneficial (in the case of therapeutic) response could be initiated by the human microbiome. In this sense, we would create an active probiotic.
We will demonstrate a cation responsive genetic sensor by regulating expression of GFP using the sodium responsive transcriptional regulator, NhaR. NhaR binds to the promoter region for the pgaA gene naturally regulating transcription of the pgaABCD operon. We will use the ionophore monensin, known to create a change in Na+ equilibrium across the cell membrane, as a proxy to imitate an ionic response within a biofilm. This proof of concept experiment will result in two new iGEM parts, the NhaR transcription factor and the pgaA promoter.
Learn more about our project on our Project Page where we show detailed laboratory procedures and notes from our project.
Learn more about our mathematical models on our Modeling Page where we introduce our models for the project.
Applications
The protein within the plasmid backbone of bacteria natural to the human microbiome could be used as a therapeutic drug to protect people from possible toxicants in the environment by sensing their harmful effects within biofilms and host cells or as a therapeutic drug to enhance someone’s natural microbiome by beneficial ionic responses with biofilm formation. For example, it could be taken and used to coat the insides of the respiratory tract to detect changes and prevent unregulated ion channels. This in turn could prevent serious bodily harm with minimal disturbance of ion balance/ biofilms and could enhance microbiome response overall.
Protective biofilms throughout your body
Bacteria communicate with each other and the host cells
Create a sensor for ions for cell to cell communications in a medically relevant way
Out on the battlefield and expect to be exposed
What’s the response from the respiratory tract
Cell-cell communication within biofilms and with the host using ions within the human body
Risks
Our modified organism could pose the risk of environmental release, if applied to the human body. We will need to engineer in a kill-switch mechanism, or another self-destruct mechanism to control unintended proliferation. Our team also discussed the harsh facts in the field of synthetic biology as it relates to the military, in that, one could engineer a biological organism for nefarious purposes. While many advances in synthetic biology have been focused on the positives such as, improving upon pre-existing shortcomings occurring in nature, some minds may focus on the fact that bad people could use synthetic biology techniques for nefarious purposes. He agreed with us that there is a misconception among the civilian population on how the military actually uses these biological advances. It is important to note that the military is using synthetic biology to defend our sailors and marines from harmful substances and not the otherway around.
