Role of Thioarsenic Compounds in As(III) Oxidation in an Alkaline Lake

University Of Georgia Research Foundation Inc, Athens GA

Investigators

Abstract

This research will seek to elucidate the pathway for thioarsenate decomposition by microbial assemblages, using alkaline, sulfidic and arsenic-enriched Mono Lake bottom waters as a study site. Enrichment cultures and manipulation experiments will be performed to test the effects of different electron acceptors on thioarsenate decomposition. The PI will analyze the microbial communities to determine which organisms and which enzyme systems respond to enrichments with thioarsenates to aid in identifying pathways. These experiments are designed to address the following questions: 1) What is the behavior of thioarsenate with arsenate, nitrate or oxygen as electron acceptors? Are there specific groups of microbes associated with each pair of reactants? 2) What are the products of the reaction? 3) How does gene expression change during thioarsenate decomposition? What are the pathways involved in thioarsenate oxidation? The results of this study will be relevant, not only for a better understanding arsenic cycling in Mono Lake, but for modeling arsenic in other neutral or alkaline environments where arsenite and sulfide are present and exposed to changing redox conditions. Thioarsenate transformation may be of particular importance in alkaline hot springs, industrial waste sites, or aquifers with bedrock containing arsenic- and sulfur-bearing minerals. One outcome will be a better understanding of arsenic transformations and mobility under fluctuating redox conditions in anoxic groundwater. The information may also be useful in designing bioremediation strategies. The proposed studies are also relevant to understanding and modeling the role of arsenic in the early stages of the evolution of life on Earth.