Examining the Influence of Arsenite on Microbial Metabolism.

The United Nations designated 2005-2015 as an International Decade for Action: ‘Water for Life’, with the intent of focusing attention of world governments on the declining availability of freshwater fit for human use. The severe arsenic contamination crisis in much of Asia is the most high profile example of soil and water contamination, though there are regions in the United States that also suffer from elevated arsenic, resulting in real economic implications for land and water resource managers in agriculture, mine reclamation, and municipal water treatment.  The fate, mobility, and ecotoxicology of arsenic in soil and water are highly dependent on microbial processes that regulate arsenite (As^III, most toxic) oxidation and arsenate (As^V) reduction, and thus for reliable prediction of how and why arsenic moves within and across environments it is essential that microbe-arsenic interactions be understood in detail.

We study Agrobacterium tumefaciens strain 5A, which was isolated from an arsenic-impacted soil.  It qualifies as a model bacterium for this type of research because it is representative of microorganisms routinely isolated from arsenic-contaminated soils worldwide and it is genetically tractable. Thus, it represents an ecologically–relevant organism that can be manipulated genetically for studies aimed at predicting how and why bacterial metabolism is influenced and disrupted by As^III.  Of particular interest, we wish to determine the broader implications for carbon and nitrogen cycling in the environment.   Our current work examines the three known bacterial As^III sensing systems for their influence on gene expression patterns (specific reporter genes and RNA-Seq) as well as metabolomics to assess genotype specific metabolic profiles.  Our goal is to define the full effects of As^III, linking gene expression to actual metabolism and cell behavior.  The current state of these research thrusts will be discussed.