PECASE: Mercury Methylation in Sulfate-Reducing Biofilms

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0348783JayMercury (Hg) contamination of food chains is a worldwide problem, posing public health threats even in pristine areas. In aquatic systems, mercury methylation is a key process, whereby less-toxic inorganic mercury is microbially transformed to methylmercury, which is a potent neurotoxin with a strong tendency to magnify in concentration in food chains. While the process of mercury methylation is critical to understand if we are to predict or mitigate impacts due to mercury contamination, the factors controlling its rate are extremely complex. Sulfate-reducing bacteria (SRB) have been shown to be the primary mercury methylators in a wide range of aquatic systems, and bioavailability of mercury to the bacteria, as well as the activity of particular species of sulfate-reducing bacteria present, have both been shown to be important factors in controlling the rate of mercury methylation. Intellectual merit: This work addresses fundamental questions regarding the environmental factors controlling mercury methylation. This work will elucidate the effects of mercury speciation on methylation in reducing environments, the importance of the strain of sulfate-reducing bacteria, and the effects of biofilm formation on methylation in sulfate-reducing biofilms. Results from the educational innovations in service-learning will also be made available to the public via the literature and web-accessible documents. Broader impacts: Results from the proposed work are necessary for accurately modeling of the fate of mercury in the environment. Information gained can be extended to the study of other contaminants in biofilm systems, both natural and engineered. This work may also be directly applicable to wetland restoration and lake management decisions. The PI is currently working with the UCLA Center for Experiential Education and Service Learning (CEESL) to develop an innovative service-learning course in which UCLA students will learn and then teach wetland functions in grade 6 classrooms to economically disadvantaged students of Los Angeles. The teaching unit to be developed will involve four in-class laboratory sessions and will culminate in a field trip for the grade 6 students (accompanied by the UCLA students) to Ballona Wetland. A teacher training to support the wetland science curriculum will be given by the PI each summer.