Synterception is a multi-tiered biocontainment system that was designed
to be implemented by other iGEM teams to increase the security of their
engineered constructs and reduce survival of non-target organisms that
gain recombinant DNA. We were inspired to create this system because of
a previous MSU iGEM project to develop a probiotic for bees. While
carrying out this project, we learned about several gaps in current
biocontainment strategies that will serve as a barrier to implementation
of many types of iGEM projects, especially those that would require
implementation outside of a controlled environment like a lab or factory.
One major gap we identified was the lack of a robust, standardized system to prevent horizontal gene transfer of synthetic parts. Although efforts to produce a genome-recoded strain of E. coli in order to enhance biocontainment are underway, these advances are still several years ahead and are only applicable to systems that can be implemented in E. coli, which is not a practical chassis organism for all projects.
We hope that our multi-tiered biocontainment system can be implemented by other iGEM teams to increase the security of their engineered constructs and prevent unwanted horizontal gene transfer. We envision that with further development, our secure strain of E. coli can be deposited on Addgene along with a plasmid construct into which teams can integrate their genetic parts. We believe that our layering systems could be easily translated into other microbes as well for more diverse applications.
Our project is designed to be applicable to a wide variety of fields within synthetic biology, with a specific focus on allowing for the eventual release of transgenic microbes into less controlled environments while preventing native microbes from taking up the synthetic parts. We chose E. coli as our chassis due to its versatility in synthetic biology applications and thorough characterization, but we hope that the solution could be implemented in other commonly engineered microbes with minimal adaptations.
The baseline design uses the GhoST toxin/antitoxin system, in which the ghoS antitoxin gene is chromosomally integrated and under the control of a constitutive promoter, and the ghoT toxin gene is placed on the plasmid containing the gene-of interest, also constitutively expressed (see Design). However, teams that wish to include auxotrophic containment in their biocontainment system could substitute the constitutive promoter for an inducible promoter specific to their intended application, such that the antitoxin is only expressed under desirable conditions [citation on auxotrophic containment here]. This would result in an additional layer of security entirely adaptable to the team’s project. For example, in our partnership with MST-Maastricht (See Partnership), we planned a biocontainment system for their project that would place the antitoxin under the control of a hydrogen peroxide-inducible promoter, such that the microbe could only survive in anaerobic environments such as the mammalian gut and would otherwise be lysed by the toxin.