摘要： The speciation of mercury (Hg) is a major determinant of its methylation rate by sulfate-reducing bacteria (SRB), considered the primary methylators. Under anoxic conditions, sulfur (S) cycling may have a significant influence on Hg complexation and methylation, by influencing both SRB activity and the pool of available reduced S ligands, as the presence of zero-valent sulfur (S(0)) in sulfidic water results in the formation of polysulfides. While SRB frequently coexist with S-oxidizing bacteria in natural environments, the effect that these organisms may have on methylation by SRB is not understood. In this study, we investigate the role of S(0) in methylation by SRB monocultures and cocultures with phototrophic green or purple S-oxidizing bacteria. In the coculture experiments, the presence of S-oxidizers was found to increase Hg methylation rates, apparently by maintaining favorable chemical speciation in the environment. The measured Hg methylation rates were in accord with predictions based on geochemical modeling of speciation. In SRB monoculture experiments conducted in the presence and absence of S(0), the data showed that at limited total Hg, the presence of polysulfides resulted in decreased Hg methylation, presumably by causing a decrease in the most bioavailable Hg–sulfide complexes. These results indicate that models of Hg speciation and methylation in the environment should include a detailed investigation of S redox speciation. 其他題名： Water Air Soil Pollut 出版者： Dordrecht: Springer Netherlands 出版日期： 2013-02-01 出處： Water, air, and soil pollution, 2013-02, Vol.224 (2), p.1-14, Article 1399 資源來源： Agricultural & Environmental Science Collection 版權： Springer Science+Business Media Dordrecht 2012 版權： 2014 INIST-CNRS 版權： COPYRIGHT 2013 Springer 版權： Springer Science+Business Media Dordrecht 2013 識別號： ISSN: 0049-6979 識別號： EISSN: 1573-2932 識別號： DOI: 10.1007/s11270-012-1399-7 識別號： CODEN: WAPLAC
