Methylmercury decomposition in sediments and bacterial cultures: Involvement of methanogens and sulfate reducers in oxidative demethylation

Journal Article · Tue Jan 01 04:00:00 EST 1991 · Applied and Environmental Microbiology; (USA)

OSTI ID:5804167

Oremland, R S; Culbertson, C W ^[1]; Winfrey, M R ^[2]

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1. U.S. Geological Survey, Menlo Park, CA (USA)
2. Univ. of Wisconsin, La Crosse (USA)

The biogeochemical cycling of mercury has received considerable attention because of the toxicity of methylmercury, its bioaccumulation in biota, and its biomagnification in aquatic food chains. The formation of methylmercury is mediated primarily by microorganisms. Demethylation of monomethylmercury in freshwater and estuarine sediments and in bacterial cultures was investigated with {sup 14}CH{sub 3}HgI. Under anaerobiosis, results with inhibitors indicated partial involvement of both sulfate reducers and methanogens, the former dominated estuarine sediments, while both were active in freshwaters. Aerobes were the most significant demethylators in estuarine sediments, but were unimportant in freshwater sediments. Products of anaerobic demthylation were mainly {sup 14}CO{sub 2} as well as lesser amounts of {sup 14}CH{sub 4}. Acetogenic activity resulted in fixation of some {sup 14}CO{sub 2} produced from {sup 14}CH{sub 3}HgI into acetate. Aerobic demethylation in estuarine sediments produced only {sup 14}CH{sub 4}, while aerobic demethylation in freshwater sediments produced small amounts of both {sup 14}CH{sub 4} and {sup 14}CO{sub 2}. Two species of Desulfovibrio produced only traces of {sup 14}CH{sub 4} from {sup 14}CH{sub 3}HgI, while a culture of a methylotrophic methanogen formed traces of {sup 14}CO{sub 2} and {sup 14}CH{sub 4} when grown on trimethylamine in the presence of the {sup 14}CH{sub 3}HgI. These results indicate that both aerobes and anaerobes demethylate mercury in sediments, but that either group may dominate in a particular sediment type. Aerobic demethylation in the estuarine sediments appeared to proceed by the previously characterized organomercurial-lyase pathway, because methane was the sole product. This indicates the presence of an oxidative pathway, possibly one in which methylmercury serves as an analog of one-carbon substrates.

• OSTI ID: 5804167
• Journal Information: Applied and Environmental Microbiology; (USA), Journal Name: Applied and Environmental Microbiology; (USA) Vol. 57:1; ISSN 0099-2240; ISSN AEMID
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540320* -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (1990-)
550201 -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BACTERIA
BIODEGRADATION
CARBON 14 COMPOUNDS
CHEMICAL REACTIONS
DECOMPOSITION
FRESH WATER
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MERCURY COMPOUNDS
METHYLMERCURY
MICROORGANISMS
ORGANIC COMPOUNDS
ORGANIC MERCURY COMPOUNDS
OXYGEN COMPOUNDS
SEDIMENTS
SULFATE-REDUCING BACTERIA
TRACER TECHNIQUES
WATER