Research press release


Nature Chemical Biology

‘Deadman’ and ‘Passcode’ kill switches keep synthetic bacteria in check



今回の論文では、James Collinsたちが、大腸菌を効率的に死滅させることができる新しいキルスイッチ2種類を報告している。Deadmanスイッチは、連続的に発現する毒素が細胞を殺さないようにするために外的な化学物質を必要とする細菌株を作製した過去の研究に基づいており、今回は系の小回りおよび信頼性を改善する変法が報告されている。Passcodeスイッチは、転写因子タンパク質の一部分が化学シグナルに応答して別の部分が特定のDNAセグメントを制御するという複合的な転写因子を利用して、細胞の制御に利用する化学シグナルをうまく組み合わせることができる。Collinsたちは、このカスタマイズにより、求める特定の用途に従って細菌を仕立てることができると指摘する。


Two new containment strategies to keep genetically modified bacteria from escaping into the environment are reported in a study published online this week in Nature Chemical Biology. The synthetic gene circuits-called ‘Deadman’ and ‘Passcode’-are customizable and may have a variety of industrial and environmental applications.

Genetically engineered bacteria can potentially be used to accomplish a range of important tasks, such as monitoring toxins in rivers and improving crop fertilization. However, before modified cells are used in these ‘real world’ scenarios, scientists also want to make sure that the cells cannot grow on their own, which could disrupt native environments. This kind of control mechanism is typically called a ‘kill switch’ as the bacteria are meant to die without a necessary input provided by the scientists.

In this study, James Collins and colleagues report two new kill switches that can efficiently kill Escherichia coli. The ‘Deadman’ switch builds on past work creating a bacterial strain that needs an external chemical to prevent a continuously expressed toxin from killing the cell, with the alterations reported here making the system faster and more reliable. The ‘Passcode’ switch uses hybrid transcription factors, in which one section of the transcription factor protein responds to a chemical signal and another controls a specific segment of DNA, to enable researchers to mix and match the chemical signals used to control the cell. The authors note that this customization should allow researchers to tailor bacteria according to the specific application desired.

Finally, they suggest that the Passcode switch may also be particularly useful as a tool for protecting intellectual property, since unauthorized growth of bacterial strains without the appropriate passcode molecules would induce cell death.

doi: 10.1038/nchembio.1979

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