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<p class="untertitel"><i>nsc = no single colonies<br>Note: Some plates showed no colonies at the time point that the pictures were taken. Empty plates were incubated longer and counted later.</i></p> | <p class="untertitel"><i>nsc = no single colonies<br>Note: Some plates showed no colonies at the time point that the pictures were taken. Empty plates were incubated longer and counted later.</i></p> | ||
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Revision as of 16:21, 31 October 2017
Heidelberg 2017
Click on the picture to get to team Heidelberg's collaboration page.
As fellow scientists exploring the field of targeted evolution, we helped iGEM-team Heidelberg by conducting an experiment for them, to validate their results in another lab. Our colleagues used three different mutagenesis plasmids (MPs) created by A. H. Badran et al. in 2015: #1, #2 and #3, as they are named by the iGEM team. The MPs build up on each other in accession of their respective numbers.
#1 increases the mutation-rate through arabinose induces expression of dnaQ926, an ineffective E. coli DNA Pol III proofreading domain.
#2 also contains the gene encoding Dam methylase under arabinose induction, as well as the gene seqA under low-level expression. Dam methylase is crucial in mismatch-repair in E. coli, as it methylates the parental strand in DNA replication, making it distinguishable from the new daughter strand. If Dam methylase is overexpressed, the daughter strand is methylated too quickly, which impairs the mismatch-repair mechanism. seqA encodes a protein that delays the function of Dam methylase, which solves some issues of the arabinose induced promoter being not completely tight.
#3 contains the additional genes ugi, cda1 and emrR. ugi encodes cytidine deaminase, which catalyzes cytosine to tyrosine transitions and therefore causes base substitutions in the host’s genome. This transition goes through a deoxyuracil intermediate, which may be excised by uracil-DNA glycosylase during the native uracil-excision pathway. cda1 is a natural inhibitor of uracil-DNA glycosylase and therefore acts synergistically with ugi. emrR is a gene repressor for a number of different multidrug resistance pumps. The exact mechanism is unknown, but overexpression of emrR leads to a repression of those efflux pumps and therefore may lead to an increase of mutagenic pathway intermediates in the cell, increasing mutagenesis.
#1, #2 and #3 raise mutagenesis rates high enough, for E. coli to spontaneously evolve antibiotic resistances. If plated on several different antibiotics, under induction of the plasmids with arabinose, a portion of the cell population is supposed to survive with new resistances. This is what Heidelberg wants us to verify. Below is their protocol, which we followed:
Results
![](https://static.igem.org/mediawiki/2017/9/9a/T--BOKU-Vienna--Heidelberg_Results1.png)
![](https://static.igem.org/mediawiki/2017/5/5f/T--BOKU-Vienna--Heidelberg_Results2.png)
![](https://static.igem.org/mediawiki/2017/5/55/T--BOKU-Vienna--Heidelberg_Results3.png)
nsc = no single colonies
Note: Some plates showed no colonies at the time point that the pictures were taken. Empty plates were incubated longer and counted later.
Baltimore Biocrew
![](https://static.igem.org/mediawiki/2017/0/03/BioCrewTeam.jpeg)
This is the Baltimore BioCrew fighting against plastic waste. Click on their picture to get to their collaboration page.
As a potential application, our project could help clean up microplastics from the environment. Releasing GMOs and confronting the public with this topic bears several risks. We found out that the Baltimore BioCrew is working on a similar topic, sharing the same difficulties and questions. A delegation of our team flew to Baltimore and setup a meeting with the BBC. After a constructive talk and some European strudel we decided to help the Baltimore team and set up a survey to gain an insight on the thoughts of the population. Back in Europe we stayed in contact and supported the BBC whenever they had any further questions. We were very happy to support the BBC in their work and hope for ongoing collaborations in the next contests.