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There are more than a thousand Superfund sites in the United States, and many of them are located near or in neighborhoods or areas prone to earthquakes, flooding, or erosion. Superfund sites are hazardous waste dumps that have been identified by the Environmental Protection Agency (EPA) as posing an unacceptable risk to human health and the health of other organisms. The EPA has identified several chemical substances present in Superfund sites, ranging from hazardous metals to harmful organic compounds. Our team decided to focus on dichloromethane (DCM), a widely used synthetic haloalkane that is present in high concentrations at a Superfund site close to our school. DCM has wide-ranging and serious health effects; it is carcinogenic, neurotoxic, and hepatotoxic. Our goal is to create a biosensor for the detection of DCM. We are utilizing synthetic biology to design a biological system that will display red fluorescence when DCM is detected. Our system uses Escherichia coli as the chassis and is composed of two connected devices: a DCM sensor and a DCM reporter. For the DCM sensor, we are using the dcmR gene, which was first identified in the genome of Methylobacterium extorquens, a methylotrophic bacterium capable of degrading DCM. The dcmR gene, which is regulated by a constitutive promoter, produces the DcmR protein, a transcriptional repressor for the Red Fluorescent Protein (RFP) gene. When DCM is present in the samples tested, it will bind to the DcmR protein and change its conformation, derepressing the RFP gene and triggering visible red fluorescence. We are adding a tuner in order to link the intensity of the red fluorescence to the varying DCM concentration. Compared with the conventional analytical methods for DCM detection, this biological system provides an inexpensive and easy-to-use DCM biosensor for testing water and soil samples from Superfund sites.

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