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The ethics of biological kill switches

Imagine if I told you that there were ways within our reach to fix so many problems which have plagued us for centuries. Imagine that in a year, we could stop diseases like Malaria, Ebola, Anthrax, Late Blight, and many others from spreading and infecting countless species. You would call me crazy, right? A straight up lunatic.

I’ll start off by introducing myself. I’m Amr Ghazal, a twenty-two-year-old Mathematics major at Lunds University, Sweden. As to what business I have talked about preventing diseases, it would be attributed to my two-year engagement with synthetic biology through iGEM. I joined iGEM in 2019 without any prior knowledge related to gene editing or synthetic biology. However, in a short period of time, I managed to learn a lot about the topics and engage with large groups of people that are passionate about it. To those people who are devoted to synthetic biology, nothing seems impossible. The sky is never the limit. Dumbed down, synthetic biology involves manipulating a certain strain of bacteria or algae to produce our desired protein and keep doing so by consuming sugar. This application extends into many complex systems and has multiple shapes and structures. But sadly, something often gets in the way of these scientists’ ambitions and dreams. It is partly outdated laws and legislations, and sometimes hidden political agendas. In many regions, such as Europe for example, it is almost forbidden to release genetically modified organisms into the environment. These laws and their strictness have curbed and curtailed the progression and development of many fields such as agriculture and medicine.



Designing and releasing GMO’s into the environment is a matter that requires the utmost proficiency and carefulness, as one mistake can cause an irretrievable chain reaction that would harm and destroy several ecosystems and humans alike. Therefore, before attempting to release any modified organism, there must be several measures taken to minimize the risks of doing such a thing. Needless to say, the first steps would be performing numerous and rigorous experiments to assess the level of risk that is accompanied by such a task. The organism itself carrying our edited gene is, if cleverly designed, harmless and poses no risk to an ecosystem. However, over time and many reproductive cycles, our modified organism can mutate into a harmful one. Which is why once the preliminary experimentation is done on the GMO, we move to a phase of designing a kill switch for it.


A kill switch essentially decides under which circumstances a GMO should survive or die. It can be customized and appropriated for each different bacterium. Fundamentally, setting up a kill switch in a modified organism means using a gene circuit that either maintains essential gene expression or blocks a toxin gene expression circumstantially based on certain biocontainment conditions. Which means that


once a kill switch is activated, if it is in charge of halting the function of a vital gene, the organism will not be able to reproduce.

On the other hand, if its activation increases the expression of a deadly gene that would harm the modified organism, it will release a harmful toxin that in turn would kill the bacteria thus ending its life cycle. Different variations of the same method have been proven to be successful in preventing the further growth and reproduction of a mutated and harmful bacteria (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5812007/).



We can take a look at two kill switches designed for Escherichia coli bacteria called “Deadman” and “Passcode”. The “Deadman” kill switch relies on a transcription-based monostable toggle design to ensure a swift and efficient elimination of cells. The circuit allows the cell to survive by using small molecule-binding transcription factors that repress toxin production in the presence of a certain environmental signal. If the signal were to be removed, the depressed toxin production would wind up killing the cells. However, it is not as easy as it sounds. For this kill switch to work, it required the alteration of ribosome binding site strengths of LacI and TetR to favor TetR expression in a single-copy plasmid. The resulting monostable circuit needs to be in a state that contains an abundance of LacI+ for it to survive. In addition to that, incorporating toxin genes into the TetR+ state further supplements the necessity of ATc - the TetR inhibitor. To prevent the de-repressed toxin production and cell death, constant production of ATc is required. Therefore, a kill switch that is dependent on ATc is created. The Passcode circuit, however, relies on hybrid LacI-GalR family transcription factors to construct complex environmental requirements for cell survival. Due to the orthogonality of the hybrid DRMs and ESMs, a serial arrangement of Passcode circuits that respond to specific combinations of environmental inputs was made possible. The toxin production in these circuits is repressed by a transcription factor called Hybrid C whose expression is reliant on the presence of two other transcription factors called Hybrid A and Hybrid B. Thus, the loss on an input that produces Hybrid A or Hybrid B will lead to the cell death. These two kill switches are prime examples of methods to eliminate unwanted reproduction of modified organisms. (https://pubmed.ncbi.nlm.nih.gov/26641934/)


With there being a way for us to combat the main risk that comes along releasing GMO’s to the environment, it is about time we update our current laws and tailor them to our situation. GMO’s can be released into the environment safely if the right procedures are carried out. Which is why these laws have to be changed to ones that make sure anyone attempting to release GMO’s follows the right steps and procedures and maintains a certain level of carefulness.



iGEM Lund 2020



“The iGEM Lund team for this year comprises of aspiring scientists from different study fields. Our project, Protecto, aims to solve a common problem that potato farmers face on a daily basis. By producing recombinant antimicrobial peptides (AMPs) and a two-plasmid system, we intend to offer a solution for the Late Blight Disease or otherwise known as phytophthora which infects potato plants regularly. We also wanted to incorporate an optically regulated (optogenetic) kill switch to offer the possibility of scaling this project into future markets.”


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Image source (1): https://news.mit.edu/2015/kill-switches-shut-down-engineered-bacteria-1211