scholarly journals Mercury methylation in Sphagnum moss mats and its association with sulfate-reducing bacteria in an acidic Adirondack forest lake wetland

2010 ◽  
Vol 74 (3) ◽  
pp. 655-668 ◽  
Author(s):  
Ri-Qing Yu ◽  
Isaac Adatto ◽  
Mario R. Montesdeoca ◽  
Charles T. Driscoll ◽  
Mark E. Hines ◽  
...  
Keyword(s):  
Sulfate Reducing Bacteria ◽  
Mercury Methylation ◽  
Sphagnum Moss ◽  
Sulfate Reducing ◽  
Forest Lake ◽  
Reducing Bacteria

scholarly journals Mercury Methylation by Dissimilatory Iron-Reducing Bacteria

2006 ◽  
Vol 72 (12) ◽  
pp. 7919-7921 ◽  
Author(s):  
E. J. Kerin ◽  
C. C. Gilmour ◽  
E. Roden ◽  
M. T. Suzuki ◽  
J. D. Coates ◽  
...  
Keyword(s):  
Sulfate Reducing Bacteria ◽  
Culture Conditions ◽  
Mercury Methylation ◽  
Iron Reducing Bacteria ◽  
Sulfate Reducing ◽  
Abiotic Controls ◽  
Reducing Bacteria

ABSTRACT The Hg-methylating ability of dissimilatory iron-reducing bacteria in the genera Geobacter, Desulfuromonas, and Shewanella was examined. All of the Geobacter and Desulfuromonas strains tested methylated mercury while reducing Fe(III), nitrate, or fumarate. In contrast, none of the Shewanella strains produced methylmercury at higher levels than abiotic controls under similar culture conditions. Geobacter and Desulfuromonas are closely related to known Hg-methylating sulfate-reducing bacteria within the Deltaproteobacteria.

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

2000 ◽  
Vol 66 (6) ◽  
pp. 2430-2437 ◽  
Author(s):  
Jeffrey K. King ◽  
Joel E. Kostka ◽  
Marc E. Frischer ◽  
F. Michael Saunders
Keyword(s):  
Sulfate Reduction ◽  
Marine Sediments ◽  
Marine Sediment ◽  
Pure Culture ◽  
Sulfate Reducing Bacteria ◽  
Mercury Methylation ◽  
Sulfate Reducing ◽  
The Family ◽  
Pure Cultures ◽  
Reducing Bacteria

ABSTRACT Differences in methylmercury (CH3Hg) production normalized to the sulfate reduction rate (SRR) in various species of sulfate-reducing bacteria (SRB) were quantified in pure cultures and in marine sediment slurries in order to determine if SRB strains which differ phylogenetically methylate mercury (Hg) at similar rates. Cultures representing five genera of the SRB (Desulfovibrio desulfuricans, Desulfobulbus propionicus,Desulfococcus multivorans, Desulfobacter sp. strain BG-8, and Desulfobacterium sp. strain BG-33) were grown in a strictly anoxic, minimal medium that received a dose of inorganic Hg 120 h after inoculation. The mercury methylation rates (MMR) normalized per cell were up to 3 orders of magnitude higher in pure cultures of members of SRB groups capable of acetate utilization (e.g., the family Desulfobacteriaceae) than in pure cultures of members of groups that are not able to use acetate (e.g., the family Desulfovibrionaceae). Little or no Hg methylation was observed in cultures of Desulfobacterium orDesulfovibrio strains in the absence of sulfate, indicating that Hg methylation was coupled to respiration in these strains. Mercury methylation, sulfate reduction, and the identities of sulfate-reducing bacteria in marine sediment slurries were also studied. Sulfate-reducing consortia were identified by using group-specific oligonucleotide probes that targeted the 16S rRNA molecule. Acetate-amended slurries, which were dominated by members of the Desulfobacterium and Desulfobacter groups, exhibited a pronounced ability to methylate Hg when the MMR were normalized to the SRR, while lactate-amended and control slurries had normalized MMR that were not statistically different. Collectively, the results of pure-culture and amended-sediment experiments suggest that members of the family Desulfobacteriaceae have a greater potential to methylate Hg than members of the familyDesulfovibrionaceae have when the MMR are normalized to the SRR. Hg methylation potential may be related to genetic composition and/or carbon metabolism in the SRB. Furthermore, we found that in marine sediments that are rich in organic matter and dissolved sulfide rapid CH3Hg accumulation is coupled to rapid sulfate reduction. The observations described above have broad implications for understanding the control of CH3Hg formation and for developing remediation strategies for Hg-contaminated sediments.

scholarly journals Mercury Methylation from Unexpected Sources: Molybdate-Inhibited Freshwater Sediments and an Iron-Reducing Bacterium

2006 ◽  
Vol 72 (1) ◽  
pp. 457-464 ◽  
Author(s):  
Emily J. Fleming ◽  
E. Erin Mack ◽  
Peter G. Green ◽  
Douglas C. Nelson
Keyword(s):  
Specific Inhibitor ◽  
Sulfate Reducing Bacteria ◽  
Mercury Methylation ◽  
Clear Lake ◽  
Freshwater Sediments ◽  
Iron Reducing Bacteria ◽  
Sulfate Reducing ◽  
Environmental Toxin ◽  
Reducing Bacteria ◽  
First Time

ABSTRACT Methylmercury has been thought to be produced predominantly by sulfate-reducing bacteria in anoxic sediments. Here we show that in circumneutral pH sediments (Clear Lake, CA) application of a specific inhibitor of sulfate-reducing bacteria at appropriate concentrations typically inhibited less than one-half of all anaerobic methylation of added divalent mercury. This suggests that one or more additional groups of microbes are active methylators in these sediments impacted by a nearby abandoned mercury mine. From Clear Lake sediments, we isolated the iron-reducing bacterium Geobacter sp. strain CLFeRB, which can methylate mercury at a rate comparable to Desulfobulbus propionicus strain 1pr3, a sulfate-reducing bacterium known to be an active methylator. This is the first time that an iron-reducing bacterium has been shown to methylate mercury at environmentally significant rates. We suggest that mercury methylation by iron-reducing bacteria represents a previously unidentified and potentially significant source of this environmental toxin in iron-rich freshwater sediments.

scholarly journals Methanogens and Iron-Reducing Bacteria: the Overlooked Members of Mercury-Methylating Microbial Communities in Boreal Lakes

2018 ◽  
Vol 84 (23) ◽  
Author(s):  
Andrea G. Bravo ◽  
Sari Peura ◽  
Moritz Buck ◽  
Omneya Ahmed ◽  
Alejandro Mateos-Rivera ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Lake Sediments ◽  
Aquatic Ecosystems ◽  
Sulfate Reducing Bacteria ◽  
Boreal Lakes ◽  
Mercury Methylation ◽  
Content Type ◽  
Iron Reducing Bacteria ◽  
Sulfate Reducing ◽  
Reducing Bacteria

ABSTRACTMethylmercury is a potent human neurotoxin which biomagnifies in aquatic food webs. Although anaerobic microorganisms containing thehgcAgene potentially mediate the formation of methylmercury in natural environments, the diversity of these mercury-methylating microbial communities remains largely unexplored. Previous studies have implicated sulfate-reducing bacteria as the main mercury methylators in aquatic ecosystems. In the present study, we characterized the diversity of mercury-methylating microbial communities of boreal lake sediments using high-throughput sequencing of 16S rRNA andhgcAgenes. Our results show that in the lake sediments,MethanomicrobialesandGeobacteraceaealso represent abundant members of the mercury-methylating communities. In fact, incubation experiments with a mercury isotopic tracer and molybdate revealed that only between 38% and 45% of mercury methylation was attributed to sulfate reduction. These results suggest that methanogens and iron-reducing bacteria may contribute to more than half of the mercury methylation in boreal lakes.IMPORTANCEDespite the global awareness that mercury, and methylmercury in particular, is a neurotoxin to which millions of people continue to be exposed, there are sizable gaps in the understanding of the processes and organisms involved in methylmercury formation in aquatic ecosystems. In the present study, we shed light on the diversity of the microorganisms responsible for methylmercury formation in boreal lake sediments. All the microorganisms identified are associated with the processing of organic matter in aquatic systems. Moreover, our results show that the well-known mercury-methylating sulfate-reducing bacteria constituted only a minor portion of the potential mercury methylators. In contrast, methanogens and iron-reducing bacteria were important contributors to methylmercury formation, highlighting their role in mercury cycling in the environment.

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