Within the research community, lab safety standards are designed to contain microorganisms; however, bacteria are often engineered for use in the open environment. In particular, many IGEM projects, especially in the environmental track, are designed for use in remote or less developed parts of the world. Additionally, many bacteria are now engineered using multiple antibiotic-resistance elements. Should antibiotic resistance spread, untreatable diseases would become more prevalent. A “superbug” resistant to most antibiotics, only seen outside the US, has now found its way into the United States. This form of E. coli is resistant to the last resort antibiotic Colistin as well as multiple other antibiotics(Centers for Disease Control, 2016; Christensen, J., & Goldschmidt, D., 2016). Chloramphenicol, an antibiotic commonly used in Africa because of its low cost and relatively long shelf-life, is the required antibiotic for part submission as a BioBrick. Also, Cillins and Cyclins are commonly used in United States medical facilities as well as in synthetic biology labs. While the K-12 strain of E. coli typically used in labs is not usually pathogenic itself, it is known to exhibit lateral transfer to other, potentially pathogenic, species of bacteria (Smelt, et al., 2015; Hamada, K., Oshima, K., & Tsuji, H., 2003).
Measures must be taken to prevent both the proliferation of genetically engineered bacteria and the lateral transfer of antibiotic resistance in the environment. Our 2016 IGEM team’s goal is to build a killswitch, so that when bacteria escape the lab environment and are separated from the growth medium, it will die. We have designed a passive killswitch using the arabinose-repressible pBAD promoter driving the production of a TetR repressor. TetR will prevent the transcription of colicin. When the concentration of arabinose drops, the colicin will no longer be repressed and will kill the cell, preventing proliferation.