Low temperature anaerobic bacterial diagenesis of ferrous monosulfide to pyrite

In vitro enrichment cultures of dissimilatory sulfate-reducing bacteria pre cipitated FeS and catalyzed its transformation into FeS, at ambient tempera ture and pressure under anaerobic conditions. When compared to purely abiot ic processes, the bacterially mediated transformation was shown to be more efficient in transforming FeS into FeS,. This occurred due to the large, re active surface area available for bacterially catalyzed diagenesis, where t he biogenic FeS precursor was immobilized as a thin film (similar to 25 nm thick) on the mu m-scale bacteria. The bacteria also contained the source(s ) of sulfur for diagenesis to occur. Using a radiolabeled organic sulfur tr acer study, sulfur was released during cell autolysis and was immobilized a t the bacterial cell surface forming FeS,. The formation of FeS, occurred o n both the inner and outer surfaces of the cell envelope and represented th e first step of bacterial mineral diagenesis. Pyrite crystals, having linea r dimensions of similar to 1 mu m, grew outward from the bacterial cell sur faces. These minerals were several orders of magnitude larger in volume tha n those originating abiotically. Copyright (C) 1999 Elsevier Science Ltd.