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From 2011.igem.org

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Module 3: Gene Guard

Containment is a serious issue concerning the release of genetically modified organisms (GMOs) into the environment. To prevent horizontal gene transfer of the genes we are expressing in our chassis, we have developed a system based on the genes encoding holin, anti-holin and endolysin. We are engineering anti-holin into the genome of our chassis, where it acts as an anti-toxin, and holin and endolysin on plasmid DNA. In the event of horizontal gene transfer with a soil bacterium, holin and endolysin will be transferred without anti-holin, rendering the recipient cell non-viable and effectively containing the Auxin Xpress and Phyto-Route genes in our chassis.

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Overview

For human practices to inform the design of our project, we decided to come up with a novel solution to minimising the risk of releasing GMOs into the environment. We tried to think beyond containment and "kill-switch" mechanisms and asked questions like "What would the worst-case scenario be if we were to release our GMO into the wild?" and "How can we avoid these issues?".

One of most problematic consequences of GMO release is horizontal gene transfer of non-natural plasmid DNA to existing soil bacteria, a frequently occuring process.

Gene guard is a novel mechanism to prevent horizontal gene transfer and therefore a viable solution for preventing the exchange of genetic material from GMOs to naturally occurring microbes. It will use a toxin/anti-toxin system where anti-holin is integrated into the genome of our chassis and will prevent the holin and endolysin encoded on the plasmids to lyse the cell. However, if the plasmid is transferred to any other bacterial species that is not our modified bacteria, it will induce cell lysis, thereby preventing the spread of genetic information contained in our GMO.

Alongside the assembly and testing of this module, we experimented with soil bacteria to see how long they retained fluorescence obtained from GFP-expressing E. coli by horizontal gene transfer.

For more information on our Human Practices approach to GM release click here.

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M2: Future Work M3: Specifications