Sulfate-Reducing Bacteria Methylate Mercury at Variable Rates in Pure Culture and in Marine Sediments

King, James J.; Kostka, Joel E.; Frischer, Marc E.; Saunders, F. Michael

doi:10.1128/aem.66.6.2430-2437.2000

Cited by 317 publications

(264 citation statements)

References 42 publications

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“…SRB consortia were observed at all depths sampled, but were maximal between 4 and 6 cm. Similar distribution patterns have also been observed in natural S. alterniflora-dominated salt marshes in Georgia by using the same suite of rRNA-targeted oligonucleotide probes (19,20).…”

Section: Discussionmentioning

confidence: 53%

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Whole-Cell versus Total RNA Extraction for Analysis of Microbial Community Structure with 16S rRNA-Targeted Oligonucleotide Probes in Salt Marsh Sediments

Frischer

Danforth

Healy

et al. 2000

Appl Environ Microbiol

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rRNA-targeted oligonucleotide probes have become powerful tools for describing microbial communities, but their use in sediments remains difficult. Here we describe a simple technique involving homogenization, detergents, and dispersants that allows the quantitative extraction of cells from formalin-preserved salt marsh sediments. Resulting cell extracts are amenable to membrane blotting and hybridization protocols. Using this procedure, the efficiency of cell extraction was high (95.7% ؎ 3.7% [mean ؎ standard deviation]) relative to direct DAPI (4,6-diamidino-2-phenylindole) epifluorescence cell counts for a variety of salt marsh sediments. To test the hypothesis that cells were extracted without phylogenetic bias, the relative abundance (depth distribution) of five major divisions of the gram-negative mesophilic sulfate-reducing delta proteobacteria were determined in sediments maintained in a tidal mesocosm system. A suite of six 16S rRNA-targeted oligonucleotide probes were utilized. The apparent structure of sulfate-reducing bacteria communities determined from whole-cell and RNA extracts were consistent with each other (r 2 ‫؍‬ 0.60), indicating that the whole-cell extraction and RNA extraction hybridization approaches for describing sediment microbial communities are equally robust. However, the variability associated with both methods was high and appeared to be a result of the natural heterogeneity of sediment microbial communities and methodological artifacts. The relative distribution of sulfate-reducing bacteria was similar to that observed in natural marsh systems, providing preliminary evidence that the mesocosm systems accurately simulate native marsh systems.Over the past decade, 16S rRNA-targeted specific oligonucleotide probes have become a powerful tool for describing the structure of microbial communities in a variety of natural environments (1, 35). In planktonic environments, a number of straightforward hybridization techniques are available for utilizing oligonucleotide probes, including whole-cell fluorescence in situ hybridization (1,6,16,28,29) and direct wholecell blot hybridization (2, 5). These techniques simplify the use of 16S rRNA-targeted probes and therefore allow processing of larger numbers of samples required for conducting ecologically relevant studies. However, sediment and detritus often interfere with the enumeration of bacteria, hybridization, hybridization detection, and the extraction and purification of RNA (34). Thus, probe hybridization studies of sediment samples are more difficult and time-consuming than analogous studies in planktonic environments.Despite the difficulty involved, many studies have demonstrated the utility of applying 16S rRNA probe hybridization strategies in sediment environments (3,4,7,9,10,12,17,23,24,25,30). In general, these studies have relied on hybridization of probes to RNA extracted, purified, and immobilized onto charged nylon membranes or fluorescence in situ hybridization (41). To our knowledge, no studies have utilized more straight...

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Section: Discussionmentioning

confidence: 53%

“…Hybridization and wash temperatures were previously empirically determined for each probe (8,19,20; Table 1). The blots were prehybridized in a filter-sterilized (0.2 m) hybridization solution containing 6ϫ (8,15,23).…”

Section: Methodsmentioning

confidence: 99%

Whole-Cell versus Total RNA Extraction for Analysis of Microbial Community Structure with 16S rRNA-Targeted Oligonucleotide Probes in Salt Marsh Sediments

Frischer

Danforth

Healy

et al. 2000

Appl Environ Microbiol

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“…Since the study on SRM pure-culture strains Desulfovibrio deseulfuricans first demonstrating its capacity for Hg methylation (Choi et al 1994), many studies linking Hg methylation to SRM species were conducted in natural habitats (Compeau and Bartha 1985;King et al 2000;Benoit et at. 2001;Ekstrom et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Linkage between community diversity of sulfate-reducing microorganisms and methylmercury concentration in paddy soil

Liu

Zheng

Zhang

et al. 2013

Environ Sci Pollut Res

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Sulfate-reducing microorganisms (SRM) have been thought to play a key role in mercury (Hg) methylation in anoxic environments. The current study examined the linkage between SRM abundance and diversity and contents of methylmercury (MeHg) in paddy soils collected from a historical Hg mining area in China. Soil profile samples were collected from four sites over a distance gradient downstream the Hg mining operation. Results showed that MeHg content in the soil of each site significantly decreased with the extending distance away from Hg mine. Soil MeHg content was correlated positively with abundance of SRM and the contents of organic matter (OM), NH 4 + , SO 4 2− , and Hg. The abundances of SRM based on dissimilatory (bi) sulfite reductase (dsrAB) gene at 0-40 cm depths were higher than those at 40-80 cm depth at all sites. The SRM community composition varied in the soils of different sampling sites following terminal restriction fragment length polymorphism (T-RFLP) and phylogenetic analyses, which appeared to be correlated with contents of MeHg, OM, NH 4 + , and SO 4 2− through canonical correspondence analysis. The dominant groups of SRM in the soils examined belonged to Deltaproteobacteria and some unknown SRM clusters that could have potential for Hg methylation. These results advance our understanding of the relationship between SRM and methylmercury concentration in paddy soil.

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“…3 Although many scientists have provided evidence for abiotic methylation of mercury in the environment, 4,5 it is widely accepted that biotic methylation accounts for most or all methylation in the environment, especially by sulfate-reducing bacteria (SRB). 6,7 However, the relative importance of abiotic methylation of inorganic Hg(II) should not be neglected. 3 Chemical methylation of inorganic Hg(II) can occur only if suitable methyl donors exist in the environment.…”

Section: Introductionmentioning

confidence: 99%

Methylation of inorganic mercury by methylcobalamin in aquatic systems

Chen

Wang

Yin

et al. 2007

Applied Organom Chemis

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The methylation of inorganic Hg(II) by methylcobalamin in aquatic systems was studied using high-performance liquid chromatography coupled with UV-digestion cold vapor atomic fluorescence spectrometry (HPLC-UV-CV AFS). Monomethylmercury (MMC) could be positively identified as the reaction product in the aqueous solution. The salinity and pH of the aquatic system have great effects on the formation of MMC, because they could change the species of the reactants in the solution. From an electrophile reaction point of view, salinity and pH alter the electron density of the methyl donor and the electrophilicity of metal ion in the reaction system. This methylation of inorganic Hg(II) is shown to be possible even in highly saline solutions, which indicates its importance in aquatic environments. Kinetic experiments showed that the methylation reaction was fast and first-order for Hg(II). The first-order reaction rate was determined to be 0.00612 and 0.000287 min −1 for pH 5.0 and 1.5, respectively. It is suggested that this methylation could occur in the absence of enzymes, in which Hg(II) acts as an electrophile to attack methylcobalamin with a subsequent transfer of carbanion methyl group to the higher oxidized state of Hg(II).

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Sulfate-Reducing Bacteria Methylate Mercury at Variable Rates in Pure Culture and in Marine Sediments

Cited by 317 publications

References 42 publications

Whole-Cell versus Total RNA Extraction for Analysis of Microbial Community Structure with 16S rRNA-Targeted Oligonucleotide Probes in Salt Marsh Sediments

Whole-Cell versus Total RNA Extraction for Analysis of Microbial Community Structure with 16S rRNA-Targeted Oligonucleotide Probes in Salt Marsh Sediments

Linkage between community diversity of sulfate-reducing microorganisms and methylmercury concentration in paddy soil

Methylation of inorganic mercury by methylcobalamin in aquatic systems

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