资源环境科技发展态势分析平台

The exergonic reaction of FeS with H2S to form FeS2 (pyrite) and H-2 was postulated to have operated as an early form of energy metabolism on primordial Earth. Since the Archean, sedimentary pyrite formation has played a major role in the global iron and sulfur cycles, with direct impact on the redox chemistry of the atmosphere. However, the mechanism of sedimentary pyrite formation is still being debated. We present microbial enrichment cultures which grew with FeS, H2S, and CO2 as their sole substrates to produce FeS2 and CH4. Cultures grew over periods of 3 to 8 mo to cell densities of up to 2 to 9 x 10(6) cells per m L-1. Transformation of FeS with H2S to FeS2 was followed by Fe-57 Mossbauer spectroscopy and showed a clear biological temperature profile with maximum activity at 28 degrees C and decreasing activities toward 4 degrees C and 60 degrees C. CH4 was formed concomitantly with FeS(2 )and exhibited the same temperature dependence. Addition of either penicillin or 2-bromoethanesulfonate inhibited both FeS2 and CH4 production, indicating a coupling of overall pyrite formation to methanogenesis. This hypothesis was supported by a 165 rRNA gene-based phylogenetic analysis, which identified at least one archaeal and five bacterial species. The archaeon was closely related to the hydrogenotrophic methanogen Methanospirillum stamsii, while the bacteria were most closely related to sulfate-reducing Deltaproteobacteria, as well as uncultured Firmicutes and Actinobacteria. Our results show that pyrite formation can be mediated at ambient temperature through a microbially catalyzed redox process, which may serve as a model for a postulated primordial iron-sulfur world.