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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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Specifications

As part of our human practices work, we need to consider what will happen in the event that our modified bacteria are released into the soil. The potential consequences of their release relate to their uncontrolled spread and the possibility that they pass on the auxin genes to naturally occurring soil bacteria.

The auxin compound that we are using is the natural indole-3-acetic acid, which is not used as a herbicide like many other synthetic auxins. However, in high concentrations, indole-3-acetic acid can retard plant growth - as shown in our experiments.

While there are already a few species of bacteria that are able to secrete auxin^[1], it would be careless of us to release our bacteria without giving some thought to a containment device. Initially we looked at designing a killswitch based upon the idea that the bacteria would be destroyed under certain conditions, for example, when they left the designated area. This was discarded, as creating an environment with a signal that the bacteria cannot live without would affect the delicate ecosystem of the soil.

References

[1] http://m.biotecharticles.com/Biology-Article/Natural-Growth-Hormone-IAA-Indole-3-Acetic-Acid-602.html