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

本研究将利用碱性、硫化物和富砷的Mono湖底水作为研究地点，试图阐明微生物组合分解硫砷酸盐的途径。将进行富集培养和操作实验，以测试不同电子受体对硫砷酸盐分解的影响。PI将分析微生物群落，以确定哪些生物和哪些酶系统对硫代砷酸盐的富集有反应，以帮助确定途径。这些实验旨在解决以下问题：1)当砷酸盐、硝酸盐或氧作为电子受体时，硫代砷酸盐的行为是什么？每对反应物是否都有特定的微生物群？反应的产物是什么？3)硫砷酸盐分解过程中基因表达如何变化？硫砷酸盐氧化的途径是什么？这项研究的结果不仅对更好地了解Mono湖中的砷循环具有重要意义，而且对其他存在亚砷酸盐和硫化物并暴露于不断变化的氧化还原条件下的中性或碱性环境中的砷进行建模也具有重要意义。在碱性温泉、工业废料场或基岩含有含砷和含硫矿物的含水层中，硫酸盐的转化可能特别重要。一个结果将是更好地了解砷在缺氧地下水中波动氧化还原条件下的转化和流动性。这些信息也可能对设计生物修复策略有用。拟议的研究也与理解和模拟砷在地球生命进化的早期阶段的作用有关。

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.