Members of the Hansel lab are broadly interested in the interactions between microorganisms, metals, and minerals. Coupling lab- and field-based studies, we aim to identify the enzymatic and geochemical mechanisms responsible for metal speciation and the formation/dissolution of minerals within various environments ranging from coastal estuaries to the deep sea. Our research has revealed the importance of microbial metabolites (e.g., reactive oxygen species) and reactive intermediates (e.g., thiosulfate) in the redox cycling and mineralization of metals, specifically iron, manganese and mercury. We therefore also explore the biochemical pathways responsible for formation of reactive metabolites and the regulation of these processes as a function of microbial interactions (e.g., phytoplankton-heterotrophic interfaces) and geochemical gradients (e.g., hypoxia, temperature, light). To explore these interactions, we take a multi-disciplinary approach, including metabolic/proteomic analysis of natural and chemostat grown microbial populations under various biogeochemical conditions, mutagenesis of putative enzymes within model organisms, geochemical modeling of reactive aqueous species, and spectroscopic/microscopic (e.g., X-ray absorption spectroscopy, electron microscopy) interrogation of mineral-microbe interfaces.