Coupled Mercury–Cell Sorption, Reduction, and Oxidation on Methylmercury Production by Geobacter sulfurreducens PCA

• Published in: Environmental science & technology 2014-10, Vol.48 (20), p.11969-11976
• Main Authors: Lin, Hui, Morrell-Falvey, Jennifer L, Rao, Balaji, Liang, Liyuan, Gu, Baohua
• Format: Article
• Language: English
• Subjects: Adsorption; Anaerobiosis; Bacteriology; BASIC BIOLOGICAL SCIENCES; Bioassays; Biological and medical sciences; Cellular biology; Cytochrome c Group - genetics; Cytochrome c Group - metabolism; Cytotoxicity; Desulfovibrio desulfuricans; Fundamental and applied biological sciences. Psychology; Geobacter - drug effects; Geobacter - genetics; Geobacter - metabolism; Geobacter sulfurreducens; Gram-negative bacteria; Mercury - chemistry; Mercury - metabolism; Metabolism. Enzymes; Methylation; Methylmercury Compounds - metabolism; Microbiology; Oxidation; Oxidation-Reduction; Sorption; Sulfhydryl Compounds - metabolism; Zinc - metabolism
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es502537a

G. sulfurreducens PCA cells have been shown to reduce, sorb, and methylate Hg(II) species, but it is unclear whether this organism can oxidize and methylate dissolved elemental Hg(0) as shown for Desulfovibrio desulfuricans ND132. Using Hg(II) and Hg(0) separately as Hg sources in washed cell assays in phosphate buffered saline (pH 7.4), we report how cell-mediated Hg reduction and oxidation compete or synergize with sorption, thus affecting the production of toxic methylmercury by PCA cells. Methylation is found to be positively correlated to Hg sorption (r = 0.73) but negatively correlated to Hg reduction (r = −0.62). These reactions depend on the Hg and cell concentrations or the ratio of Hg to cellular thiols (−SH). Oxidation and methylation of Hg(0) are favored at relatively low Hg to cell–SH molar ratios (e.g.,