An EXAFS study of zinc coordination in microbial cells

Five microbes were isolated from metal amended enrichment cultures derived from the sediments of a lake contaminated by a zinc smelter. Each of these organisms was grown in pure culture in the presence of zinc. Quick Extended X-ray Absorption Fine Structure (QEXAFS) spectroscopy was used to investig ate the average coordination environment of the zinc associated with the mi crobial biomass. Fitting of the first coordination shell of zinc shows that significant differences exist for each microbial species examined. The coo rdination environment of zinc varies between sulfurs to six-fold nitrogen/o xygen, with two microbial strains showing mixed coordination shells. Furthe r study is required in order to characterize these sites and their location s within the cell.