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 this problem, though there are regions in the United States that also suffer from elevated arsenic in drinking water supplies. The fate, mobility, and ecotoxicology of arsenic in soil and water is highly dependent on the abiotic and biotic processes that regulate arsenic biogeochemical cycling in nature. It is now known that microbially catalyzed redox transformations are very important in controlling arsenic chemistry in most environments, 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. The information generated from this study is expected to be of value to land and water resource managers in agriculture, mine reclamation, and municipal water treatment, finding application to bioremediation efforts aimed at manipulating microbe-As interactions in the environment and thus controlling As fate and transport. The project will include training opportunities for two Ph.D. graduate students that will include an international lab rotation in China, as well as undergraduate research internships targeting Native American students. In addition, the PIs will work with K-12 teachers to expand public and private school curricula by offering class period lectures and day-long microscopy based exercises that emphasize the importance of microorganisms to environmental health and function.
Research momentum established from previous NSF funding has now led to next-generation studies in this project that aim to comprehensively define how microbes react to arsenite in terms of total gene expression and how that then translates into perturbation of cellular biochemical pathways. The project focuses on an environmentally relevant bacterium, using specific strains that are defective in key genes that encode functions associated with arsenite detecting and regulating gene expression responses to arsenite. The organism to be studied, A. tumefaciens strain5A, is representative of microorganisms routinely isolated from arsenic-contaminated environments worldwide. By comparing arsenite responses of these strains to the original wild-type organism, the PIs will be able to define the different cellular response circuits, and how they are different or integrated. There are three objectives that frame the research. Objective 1 will use RNA-Seq technology to characterize the complete transcriptional circuit board of the three major AsIII sensing systems. Objective 2 will employ metabolomics to characterize metabolite profiles for the same microbial genotypes in order to define the full effects of AsIII on bacterial cell metabolism and to link gene expression to actual metabolism and cell behavior. Objective 3 efforts will use computational methods to integrate the metabolomics and transcriptomics data into a cellular systems format for predicting and interpreting metabolic strategies and electron fates as a function of AsIII exposure. Data generated from this study will have immediate, foundational impacts on our understanding of how bacteria react to metal(loids) in their environment, whether the environment is mine tailings, groundwater or soil.
