Safety

With the help of human practice, our project has been iteratively updated from the first two modules to the last four modules, and has designed a sophisticated and highly compatible suicide switch. In this process, we followed iGEM's security policy and whitelist requirements, and we thought deeply about which chassis creatures we could use. As for organism/part/activity that is not in the white list, we have carefully thought it out, and some of them have been check-in, and made sure that they are approved before doing it, or making adjustments in time.

Multifunctional kill switch

Prevent leakage of engineered microorganisms into the environment was important for biosafety. Besides regular approach of waste treatment, our two systems both contain a "suicide" part.




Kill switch for food-related chassis

For the food producing engineered yeast system, we designed vanillic acid-controlled suicide switch. Vanillic acid is a FDA-approved food addictive. Based on our design, expression of toxin is inhibited by TetR, and its expression is upstreamly inhibited by VanR. During the production process, vanillic acid will be added. It can release the inhibition of VanR to PvanCC, therefore expression of TetR will be strong, and it can inhibit the expression of toxin, and cell will not be kill. If engineer strain was released to the environment accidentally, without the presence of Vanillic acid, the VanR will express the expression of tetR, and expression of toxin will be strong, so strain will be kill.






Kill switch for environment-related chassis （插入Part的序号和链接）

When applying engineered bacteria into the environment for treatment, a safety system is essential to confine the bacteria to their intended environment and prevent them from affecting the normal microbial community after treatment.

Our new design includes using KillRed as a suicide switch, which releases reactive oxygen species to eliminate bacteria in a normal environment. We employ the Cre-loxP system to regulate KillRed's expression. Cre is a cyclization recombinase that interacts with loxP sites to reverse the DNA sequence between them when the sites are inverted. After incorporating a specific "sensor"—an inducible promoter triggered only in the intended environment, such as high salt concentration or low oxygen levels. This controls Cre, with the inducible promoter (Pinducible) determined by the environmental factors relevant to the application.

So when we put the strain in an environment that needs to be improved, Cre will flip the promoter upstream of KillRed, so that Killred will not be expressed and the bacteria will not be killed by sunlight. At the same time, the promoter was flipped, and the expression of population control device (BBa_K3893030) was turned on to control the population number of bacteria.



We believe that the design of these two suicide switches can serve as a reference for other iGEM teams, and they effectively address the risk of leakage of synthetic biology strains in both food and environmental topics.




Chassis safety

In our project, the strains we manipulated were Escherichia coli DH5α, Synechococcus elongatus 7942, Saccharomyces cerevisiae CEN.PK2-1C. These are all the model strains reported in literature and have a high safety guarantee. These microorganisms are classified in risk group 1; they present low risk for human safety and the environment.




Lab safety

We follow the lab handbook and strictly enforce the regulations