I am a Professor in the Departments of Earth and Planetary Science and Environmental Science, Policy, and Management at UC Berkeley, and have a faculty appointment in Materials Science and Engineering. I also have appointments in the geochemistry group of Earth and Environmental Sciences, and in the Environmental Genomics & Systems Biology Division at Lawrence Berkeley National Laboratory. My research interests are in geomicrobiology, which is the study of how microorganisms shape, and are shaped by, their natural environments. My research group studies microbial communities, primarily using cultivation-independent approaches such as genome-resolved metagenomics, metatranscriptomics, metaproteomics and metabolomics. We work on microbial dissolution and precipitation of minerals, the structure, properties and reactivity of clay minerals and nanoparticles (many of which are formed by microorganisms), microbial ecology, and microbial evolution. Many of our projects are tied to field sites. Current study locations include the Angelo Coastal Reserve and a groundwater site in the central valley (northern California), the Rifle site and East River watershed (Colorado) and Crystal Geyser (Utah). We also conduct laboratory experiments in microcosms designed to probe ecosystem processes and bioremediation treatments.