Lighting genes II

by Bio! México

Lighting genes II
iGEM Lighters 2004-2009

Light induction has inspired many iGEM projects and the competitors’ creativity has given birth to very interesting ideas, beginning with the work of the students from the University of Texas at Austin in 2004.

Team UT Austin 2004

Team UT Austin 20042005 and 2006

In the first years of the iGEM competition, the UT students used the EnvZ-Cph1 developed by Dr. Levskaya and built a bacterial lawn were the words “Hello world” were photographed. In the 2005 iGEM edition, the team attempted to build an edge detector. Finally, in the 2006 iGEM edition, they also gave some instruction about how to build a light cannon of our own. 

Other teams that also worked with light in 2006, were Chiba (with a balloon-E. coli) and ETH Zurich.

In 2007, team Calgary attempted to build an E. coli printer, which consisted on a bacterial strain capable of synthesizing agarase (an agar-degrading enzyme) in response to a light stimulus. Nevertheless, as in the case of too many iGEM projects, time went out and they only could make some construction characterizations. Team Calgary 2007 made also some contributions to the Registry, like their agarase gene.

Something similar happened to the other teams that aimed to work with light induction that year; they all had some troubles when getting their photoreceptor systems to work: team CSHL had committed to make the fruit fly Drosophila melanogaster change its behavior in response to light, through light-controlled neurotransmitter synthesis (a very interesting work line, about which there are some reports available ); team Melbourne purposed to make an E. coli strain capable of forming cell aggregates in response to two different light stimuli, with the intention of building light-molded organic scaffolds that may have some application in tissue engineering; finally, team Freiburg purposed to build a red light/far-red light switch with the PhyA phytochrome systems in E. coli.

In 2008, the Imperial College team settled a similar goal as team Melbourne 2007, but using a Bacillus subitilis chassis by overexpressing its own photoreceptor YtvA and arresting cell motility as a response to a light stimulus, promoting biomaterial synthesis at the same time. This team won a gold medal and the Best Manufacture Project and the Best Natural BioBrick Part prizes, mainly because they submitted 45 new parts for B. subtilis to the registry. That same year, team Kyoto settled among their objectives the realization of an  E. coli strain, whose flagelar movement would be regulated by light

The next year, team Sheffield purposed to generate an  E. coli capable of responding to multiple light wavelenghts with a separate reporter gene for each; but again, because of the lack of time and people, the team decided to focus on the characterization of the EnvZ-Cph1 response to light wavelenght, intensity and exposition time.

Also in 2010, team MIT attempted to build a yeast strain capable of synthesizing the chromophore phycocianobilin, which is necessary for making a functional Phy-PIF phytochrome system and that, as previously stated, has to be exogenously added to the culture medium. This team also attempted to build a light-regulated protein localization switch, that would recruit two proteins to the same intracellular compartment in response to red light. The 2010 Tokyo-NOKOGEN team is also worth noting, as they purposed to build a bacterial light-response mechanism using the EnvZ-Cph1 system and also the cyanobacterial CcaS-CcaR system.

But perhaps the most noteworthy projects from 2010 are the next three:
Team EPF Lausanne 2009
This team successfully transformed the LovTAP photoreceptor system into the BioBrick format. This kind of chimeric photoreceptor can bind directly regulate gene expression through their tryptophan-response promoter-binding domain. In other words, the LovTAP system is a one-component light-inducible system! The team also built a genetic inverter, because the LovTAP effect represses transcription at the tryptophan-response promoter, so when blue light was present, the reporter gene was increased. The team won the Best Engineered BioBrick Part prize for this great contribution.
Team Harvard 2009
This team purposed to build a light-based communication mechanism between bacterial and yeast cells: bacteria would synthesize red luciferase and the yeast cells would receive this signal through a two-hybrid photoreceptor system similar to the one published in 2002 by Dr. Shimizu-Sato and his colleagues.
Team Leuven 2009
The students from the KU Leuven team built an E. coli strain capable of synthesizing vainillin -the vanilla odor protein- in response to light. They used the YcgF blue-light sensing system that is naturally found in some E. coli strains, for which the team developed an interesting mathematical model. Finally, the team KU Leuven also employed riboregulators to control the quantity of expressed vainillin
Next on Bio!: iGEM Lighters 2010-2011


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