Collaborative Research: Geochemical Controls on the Microbial Regulation of Arsenic Cycling in Geothermal Systems

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Arsenic is a highly toxic inorganic element that is found naturally in the Earth's crust. As a result, certain environmental conditions can lead to the contamination of soils, watersheds and or drinking water supplies. Consequently, there is significant interest in determining the chemical and biological factors that control arsenic cycling in natural systems. In the current study, geothermal environments in Yellowstone National Park will be used as model systems to understand geochemical and microbiological controls on arsenic transformations in natural systems. The Yellowstone caldera contains an enormous diversity of different chemical environments and arsenic is an important constituent in many geothermal outflows, resulting in significant inputs of arsenic to local watersheds. This collaborative project in geochemistry, microbiology and genetics will evaluate geochemical controls on the rates of microbially-mediated arsenic transformation in geothermal systems, and employ quantitative molecular tools to determine the role of specific genes responsible for the transformation of arsenic. We expect to identify specific microorganisms with capabilities to oxidize or reduce arsenic, and that are important members of specific geothermal environments of Yellowstone National Park, depending on geochemical conditions. These results will assist in understanding the microbial contributions to global arsenic cycling. Further, this work will contribute directly to priorities of the Geobiology program including interactions between biological and geological systems, and an understanding of the role of microbiota in shaping Earth's evolutionary history.