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'Deadman' and 'Passcode' microbial kill switches for bacterial containment

Nature Chemical Biology volume 12, pages 82–86 (2016)Cite this article

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Abstract

Biocontainment systems that couple environmental sensing with circuit-based control of cell viability could be used to prevent escape of genetically modified microbes into the environment. Here we present two engineered safeguard systems known as the 'Deadman' and 'Passcode' kill switches. The Deadman kill switch uses unbalanced reciprocal transcriptional repression to couple a specific input signal with cell survival. The Passcode kill switch uses a similar two-layered transcription design and incorporates hybrid LacI-GalR family transcription factors to provide diverse and complex environmental inputs to control circuit function. These synthetic gene circuits efficiently kill Escherichia coli and can be readily reprogrammed to change their environmental inputs, regulatory architecture and killing mechanism.

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Figure 1: Deadman kill switch.
Figure 2: The fail-safe mechanism for Deadman circuit activation.
Figure 3: Passcode kill switch.
Figure 4: Long-term circuit stability.

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Acknowledgements

We thank J. Han for assistance with molecular cloning. This work was supported by funding from the Defense Threat Reduction Agency grant HDTRA1-14-1-0006, Office of Naval Research MURI grant N000141110725, Air Force Office of Scientific Research grant FA9550-14-1-0060 and the Howard Hughes Medical Institute.

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Author notes

  1. Clement T Y Chan, Jeong Wook Lee and D Ewen Cameron: These authors contributed equally to this work.

Authors and Affiliations

  1. Institute for Medical Engineering & Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA

    Clement T Y Chan, Jeong Wook Lee, D Ewen Cameron, Caleb J Bashor & James J Collins

  2. Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA

    Clement T Y Chan, Jeong Wook Lee, D Ewen Cameron, Caleb J Bashor & James J Collins

  3. Synthetic Biology Center, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA

    Clement T Y Chan, Jeong Wook Lee, D Ewen Cameron, Caleb J Bashor & James J Collins

  4. Harvard–MIT Program in Health Sciences and Technology, Cambridge, Massachusetts, USA

    James J Collins

  5. Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA

    James J Collins

  6. Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, Massachusetts, USA

    James J Collins

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  1. Clement T Y Chan
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Contributions

C.T.Y.C., J.W.L., D.E.C., C.J.B. and J.J.C. designed the study, analyzed data and wrote the paper. C.T.Y.C. and J.W.L. performed the experiments.

Corresponding author

Correspondence to James J Collins.

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The authors have filed a provisional application with the US Patent and Trademark Office on this work.

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Supplementary Results, Supplementary Figures 1–21 and Supplementary Table 1. (PDF 12918 kb)

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Chan, C., Lee, J., Cameron, D. et al. 'Deadman' and 'Passcode' microbial kill switches for bacterial containment. Nat Chem Biol 12, 82–86 (2016). https://doi.org/10.1038/nchembio.1979

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