The hazards imposed by arsenic on human health are well recognized and nowhere better exemplified than South/Southeast Asia where the consumption of arsenic contaminated ground water has resulted high incidences of skin disorders and various cancers. Arsenic is usually associated with iron oxide and other minerals in sediments. However, in the absence of oxygen, microbes can carry out iron and arsenic reduction reactions that result in arsenic release from sediments and accumulation in ground water. The contribution of iron vs. arsenate reduction to arsenic release, however, is unclear. Furthermore, our understanding of arsenic fate and transport within soils and sediments is limited by poorly understood biological and geochemical processes occurring within complex ground water flow pathways. Therefore, the overarching goal of this research is to determine how microbial metabolism impacts arsenic transport in sediments and soils. Specifically, researchers will investigate the expression of bacterial genes responsible for iron and arsenic reduction and commensurate biogeochemical processes responsible for controlling the partitioning and mobility of arsenic (along with their spatial distribution) within model systems that simulate the physical complexity of natural soils and sediments. The proposed research integrates biogeochemical and molecular genetic approaches aimed at developing a mechanistic understanding of the impacts of microbes on arsenic contamination of ground water. Because the nature of the arsenic problem is rooted in geomicrobiology, the intellectual merit of the proposed research is the generation of crucial information important to understanding the mechanism(s) leading to arsenic release or retention in sediments. The results will lead to a detailed conceptual model of how genetics and geochemical processes impact microbe-mineral interactions and arsenic fate. The broader impacts of the research will be to integrate research with teaching activities and community outreach by participating in a laboratory research mentorship program (called ACCESS) for community college students of under represented groups and a high school science summer program called COSMOS. Lastly, the collaboration will enhance and promote diversity through intercampus mentorship of minority graduate students at both Stanford and UCSC.
