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<p id="pp"> We contacted Dr Markus Gershater, the chief scientific officer at <i>Synthace Ltd</i>, to ask him what the application of kill switches might be in an industrial setting and what evidence would be satisfactory for their use. Dr Gershater gave the view that kill switches would not be as effective or economical as the physical and chemical bio-containment methods that Synthace currently employ. One of his concerns was that increasing the complexity of an industrial strain makes reproducibility and scalability more difficult. Any mis-control of the switch would incur cost as the run of that culture would die. For these reasons Dr Gershater thought that if increased containment is needed, investment in better physical containment is more effective and economical than biological methods. We decided to test how a kill switch might behave in an industrial setting by performing a continuous culture in a ministat (see <a href="https://2016.igem.org/Team:Exeter/Project#culture">here</a> for details). In this way we could test how viable a containment strategy kill switches are when used in industry.<br><br>

<p id="pp"> We contacted Dr Markus Gershater, the chief scientific officer at <i>Synthace Ltd</i>, to ask him what the application of kill switches might be in an industrial setting and what evidence would be satisfactory for their use. Dr Gershater gave the view that kill switches would not be as effective or economical as the physical and chemical bio-containment methods that Synthace currently employ. One of his concerns was that increasing the complexity of an industrial strain makes reproducibility and scalability more difficult. Any mis-control of the switch would incur cost as the run of that culture would die. For these reasons Dr Gershater thought that if increased containment is needed, investment in better physical containment is more effective and economical than biological methods. We decided to test how a kill switch might behave in an industrial setting by performing a continuous culture in a ministat (see <a href="https://2016.igem.org/Team:Exeter/Project#culture">here</a> for details). In this way we could test how viable a containment strategy kill switches are when used in industry.<br><br>

We then contacted Dr Tom Ellis  who leads research in synthetic biology and synthetic genome engineering at Imperial College London. His view was that kill switches are not necessarily inherently flawed, but they are a lot more prone to breaking by mutation than other possible mechanisms (e.g. auxotrophies). He suggested that multiple mechanisms could be combined that each have less than 1 in a billion escape rates. This would could give an escape rate of 1 in 10²⁰. As a result of this and our own ideas we designed a system that would incorporate both KillerRed, a kill switch already in the registry and KillerOrange, a new part. Both could work together to provide a more effective kill switch and provide the increased efficiency that Dr Ellis talked about. This influenced the design of the CRISPR based kill switch we had hoped to develop as we intended to test the effect of targeting multiple essential genes within the host genome instead of just one.<br><br>  

We then contacted Dr Tom Ellis  who leads research in synthetic biology and synthetic genome engineering at Imperial College London. His view was that kill switches are not necessarily inherently flawed, but they are a lot more prone to breaking by mutation than other possible mechanisms (e.g. auxotrophies). He suggested that multiple mechanisms could be combined that each have less than 1 in a billion escape rates. This would could give an escape rate of 1 in 10²⁰. As a result of this and our own ideas we designed a system that would incorporate both KillerRed, a kill switch already in the registry and KillerOrange, a new part. Both could work together to provide a more effective kill switch and provide the increased efficiency that Dr Ellis talked about. This influenced the design of the CRISPR based kill switch we had hoped to develop as we intended to test the effect of targeting multiple essential genes within the host genome instead of just one.<br><br>