Microbial iron metabolism in natural environments

The aim of this project was to assess the diversity of iron metabolizing bacteria in several ecological niches by culture-dependent and culture-independent methods. In particular, we wanted to determine whether non-phototrophic, anaerobic nitrate-dependent Fe(II)-oxidizers coexist with aerobic Fe(1I)-oxidizers and facultatively anaerobic Fe(III)-reducers in natural habitats. To this end, we sampled iron-rich sites in freshwater, estuarine and marine environments and enriched for non-phototrophic anaerobic and aerobic Fe(II)-oxidizers. The identification of the two environmentally most important facultatively anaerobic Fe(III) reducers and one aerobic heterotrophic Fe(II)-oxidizer in the sediment samples was carried out by means of fluorescent in situ hybridization (FISH). We were able to culture aerobic Fe(II) oxidizers in gradient tubes from each sample site. Nitrate-reducing Fe(TI)-oxidizers were only found in sediments from a Cranberry Bog. Geobacter, S’hewanella and Leptothrix coexist in Salt Pond at the oxic/anoxic interface. Microbial iron metabolism in natural environments Marianne Erbs & Jim Spain Introduction The significance of bacteria in the biogeochemical cycling of iron has been broadly recognized over the past two decades. In Fig. 1 the role of dissimilatory anaerobic Fe(III)-reducers as well as acidophilic and neutrophilic aerobic Fe(II)-oxidizers, anaerobic phototrophic Fe(II)-oxidizers and facultatively anaerobic nitrate-reducing Fe(11)-oxidizers in the microbial cycling of iron is shown. Microbial iron cycling