This fundemental research builds on our understanding of how bacteria impact metal and nutrient cycling in natural and anthropogenic ecosystems. We have developed a systematic approach to investigate microbial function and element stability within fluctuating redox environments. One model system has been the focus is the jarosite-group compounds (e.g. MFe3(SO4)2(OH)6). Natural and anthropogenic sources of metal hydroxysulfates are common in mine waste environments and some sediments, most often associated with the waste products or weathering reactions. Given their wide dispersal in mine waste settings, the lack of information pertaining to their potential biological (microbial) reactivity was surprising. Dr. Smeaton’s PhD work has identified specific ecotoxicity thresholds for Pb, As and Tl mobility modeling. We have significantly advanced the understanding of: i) how metal hydroxysulfate minerals and microbial-induced reductive dissolution occurs; (ii) metal sorption mechanism associated with bacteria and mineral composites; (iii) determined the biological function influencing oxygen and hydrogen sulfide flux across sediment/water interface associated with mine waste materials.