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Human Practices


Designing bacteria with the intention of allowing it to proliferate inside the human body presents a myriad of potential ethical problems. For example, a research team at Vanderbilt University recently designed a strain of bacteria capable of generating a hunger-suppressing lipid in vivo1. Given that one in three Americans is currently obese, this has the potential to significantly impact public health1. However, a person treated with these bacteria could accidentally transmit them to others via fecal exposure, thus negatively impacting other members of the population without their knowledge or consent1. Synthetic organisms may also mutate in unpredictable ways that could harm intended patients by, for example, causing infections or unexpected immune responses2.


Techniques do exist to manage these risks. In general, researchers must design methods to quickly eradicate the effector strains in case an unexpected issue arises3. For example, one research group attempting to modify oral bacteria introduced a mutation that made their strain dependent on environmental d-alanine3. The human diet contains very little of this compound, giving the researchers better control over growth3. They also added a mutation hindering the uptake of environmental DNA, thus rendering the strain less prone to transformation3. There are also more general solutions under development, such as “kill switches” that activate and automatically kill bacteria after a certain number of generations2.

While our project is still in its very early stages and mainly focused on translating the basic science and theory into a workable system, in the future, we would want to explore implementing several of these safeguards against potential ethical issues with the release of recombinant bacteria into the environment. For instance, while it is far down the line, as a step on the long path towards a probiotic that could one day be used in humans, we could add a module onto the oscillator plasmid that acts as a kill switch when the bacteria are exposed to the environment outside of the human body. Once this is complete, there would still be various hurdles to overcome, such as ensuring the bacteria with our plasmids don’t cause pathogenicity, and trials in mice similar to the Vanderbuilt hunger-suppressing project’s set-up. As we stated on our Collaboration page, we are planning to talk to other experts on sleep medicine, and the ethical implications of our project is certainly something we’d like to discuss with then.




3. Hillman, J.D., Mo, J., McDonell, E., Cvitkovitch, D. and Hillman, C.H. (2007), Modification of an effector strain for replacement therapy of dental caries to enable clinical safety trials. Journal of Applied Microbiology, 102: 1209–1219. doi: 10.1111/j.1365-2672.2007.03316.x




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