Collaborative Research: Coupled genetic, geochemical, and physical controls on arsenic mobilization

砷对人类健康造成的危害是公认的，没有比南亚/东南亚更好的例子了，在那里，饮用受砷污染的地下水导致皮肤病和各种癌症的高发。砷通常与沉积物中的氧化铁和其他矿物质有关。然而，在缺乏氧气的情况下，微生物可以进行铁和砷的还原反应，导致砷从沉积物中释放出来并积聚在地下水中。然而，铁和砷酸盐还原对砷释放的贡献尚不清楚。此外，我们对砷在土壤和沉积物中的命运和运输的理解受到复杂地下水流动途径中发生的生物和地球化学过程的限制。因此，本研究的首要目标是确定微生物代谢如何影响砷在沉积物和土壤中的运输。具体来说，研究人员将研究在模拟自然土壤和沉积物物理复杂性的模型系统中，负责铁和砷还原的细菌基因的表达，以及负责控制砷的分配和迁移（及其空间分布）的相应生物地球化学过程。拟议的研究整合了生物地球化学和分子遗传学方法，旨在发展微生物对地下水砷污染影响的机制理解。由于砷问题的本质植根于地球微生物学，因此拟议研究的智力价值在于产生对理解导致砷在沉积物中释放或保留的机制至关重要的信息。结果将导致遗传学和地球化学过程如何影响微生物-矿物相互作用和砷命运的详细概念模型。这项研究的更广泛影响将是通过参与一个针对弱势群体的社区大学生的实验室研究指导计划（称为ACCESS）和一个名为COSMOS的高中科学暑期计划，将研究与教学活动和社区外展活动结合起来。最后，该合作将通过对斯坦福大学和加州大学圣迭戈分校少数族裔研究生的校际指导来加强和促进多样性。

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.