Microorganisms have dominated the history of Earth, playing an intimate role in shaping its chemical and physical properties. Microbes continue their role as agents of biogeochemistry today as they drive a wide range of processes, including the cycling of carbon, oxygen, nitrogen, sulfur, and metals. Our research interests are focused on this interplay between the biosphere and the geosphere, examining how microbes drive geochemistry and how geochemistry in turn shapes microbial diversity, metabolism, and evolution. Many biogeochemical cycles are actively driven by genetically encoded molecules that are often carefully regulated to be produced only under certain environmental or physiological conditions. Thus an understanding of biogeochemical cycles that take place on global scales demands knowledge of dynamics that take place on molecular scales. As such, our research relies heavily on molecular-biological approaches that are closely coupled with geochemical approaches to achieve an integrated view of geomicrobiology.