Rapid microbial oxidation of arsenic (As) from the +III to +V oxidation state has been observed in the geothermally-influenced surface waters of Hot Creek Gorge, located in California's Owens Valley. This project will investigate the biochemical mechanism and ecological aspects of this microbial process. Arsenic-oxidizing strain(s) will be isolated from a mixed culture, obtained from Hot Creek, that is currently being maintained in the P.I.'s laboratory and retains the capacity to oxidize As(III). Gene probes (based on 16s-rRNA sequences) will be developed for the mixed culture and used to guide the isolation of pure culture(s) of As(III) oxidizers, to perform genetic characterization and phylogenetic classification of pure strain(s), and to determine the spatial distribution of As(III) oxidizing bacteria at the field site in Hot Creek Gorge. Biochemical studies will be performed with the isolated As(III)-oxidizing strain(s) to determine the kinetics and mechanism of microbial As(III) oxidation. Coupled laboratory and field studies will be conducted to determine whether this process is associated with detoxification or with energy acquisition. If resources allow, a preliminary evaluation will be made of the ecological consequences of the abundant microbial colonization of the surfaces of aquatic macrophytes, which was observed in previous field studies.
This proposal was part of the Environmental Geochemistry and Biogeochemistry program. It will be jointly funded by the Division of Ocean Sciences, Division of Chemistry, Division of Earth Sciences, Division of Molecular and Cellular Biosciences, and by the MPS Office of Multidisciplinary Activities.
