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From 2011.igem.org

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Human Practice

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Overview

Our team has decided to go down a novel route in tackling the human practices issues surrounding not only our project but also iGEM in general. Instead of sticking to the established routes of either proposing complete containment or relying on "kill switches" to prevent spread of GM bacteria, we have decided to engineer a containment switch that will not kill our AuxIn bacteria but all other microorganisms that take up the auxin-producing plasmid. In addition, we have consulted many experts and will conduct experiments that demonstrate the safety our device. The true scope of many iGEM projects can only be fulfilled if release is possible and we will be attempting to take a first step towards making this possible for our project.

Historically, iGEM teams have tried to control GM release via two mechanisms: complete containment and "suicide" mechanisms in which the bacteria kill themselves in the absence or presence of specific stimuli. However, when considering the eventual use of many projects – be it bioremediation (e.g. Peking 2010’s project), crop-enhancing projects (e.g. Bristol’s 2010 project) or other applications – full use of synthetic biology organisms will only be achieved by release and full containment is often not a realistic option. In addition, kill switches may be effective to an extent but they are easily selected against by evolution as they present a strong selective disadvantage. Stress defence mechanisms such as the SOS response in E coli add to this effect. In addition, transgenes can be transferred to other bacteria in the environment using naturally occurring mechanisms such as conjugation of plasmids. Finally, while it may be argued that engineered lab strains will quickly be outcompeted, bacteria with GM markers have been shown to become established in field trials (published in several papers, summary can be found on the EU website). In some cases, endurance of the bacteria in specific environments may even be desirable.

In light of these issues, we have decided to engineer Gene Guard, a containment switch that will lead to the lysis of natural soil bacteria that take up plasmid DNA from our engineered bacteria. We have consulted experts and the literature about the implications of our project and used this information to design an effective containment switch. However, we also tried to address all possible problems and complications arising from the impossibility of absolute control. Accordingly, we used the information we gathered to influence our release strategy and design.

However, we also acknowledge that this containment switch is never going to be completely effective. Accordingly, we have consulted ecologists and other experts on auxin, plants and soil to ensure that our device is as safe as possible and we can justify release. We researched other organisms such as soil microbes and earthworms that may be affected by the AuxIn bacteria and, with the help of the experts we consulted, devised experiments to test the safety and impact of many aspects of our project.