title: Role of methanogens and other bacteria in degradation of dimethyl sulfide and methanethiol in anoxic freshwater sediments.
abstract: The roles of several trophic groups of organisms (methanogens and sulfate- and nitrate-reducing bacteria) in the microbial degradation of methanethiol (MT) and dimethyl sulfide (DMS) were studied in freshwater sediments. The incubation of DMS- and MT-amended slurries revealed that methanogens are the dominant DMS and MT utilizers in sulfate-poor freshwater systems. In sediment slurries, which were depleted of sulfate, 75 micromol of DMS was stoichiometrically converted into 112 micromol of methane. The addition of methanol or MT to DMS-degrading slurries at concentrations similar to that of DMS reduced DMS degradation rates. This indicates that the methanogens in freshwater sediments, which degrade DMS, are also consumers of methanol and MT. To verify whether a competition between sulfate-reducing and methanogenic bacteria for DMS or MT takes place in sulfate-rich freshwater systems, the effects of sulfate and inhibitors, like bromoethanesulfonic acid, molybdate, and tungstate, on the degradation of MT and DMS were studied. The results for these sulfate-rich and sulfate-amended slurry incubations clearly demonstrated that besides methanogens, sulfate-reducing bacteria take part in MT and DMS degradation in freshwater sediments, provided that sulfate is available. The possible involvement of an interspecies hydrogen transfer in these processes is discussed. In general, our study provides evidence for methanogenesis as a major sink for MT and DMS in freshwater sediments.
authors.affiliation: Department of Microbiology and Evolutionary Biology, Faculty of Science, University of Nijmegen, NL-6525 ED Nijmegen, The Netherlands. bartl@sci.kun.nl
authors.forename: B P
authors.initials: BP
authors.lastname: Lomans
authors.forename: H J
authors.initials: HJ
authors.lastname: Op den Camp
authors.forename: A
authors.initials: A
authors.lastname: Pol
authors.forename: C
authors.initials: C
authors.lastname: van der Drift
authors.forename: G D
authors.initials: GD
authors.lastname: Vogels
mesh_terms: D000693:Anaerobiosis; D001421:Bacteria, Anaerobic / Q000187:drug effects / Q000378:metabolism*; D001673:Biodegradation, Environmental / Q000187:drug effects; D004121:Dimethyl Sulfoxide / Q000378:metabolism*; D019605:Euryarchaeota / Q000187:drug effects / Q000378:metabolism*; D005618:Fresh Water / Q000382:microbiology; D019015:Geologic Sediments / Q000382:microbiology; D006859:Hydrogen / Q000494:pharmacology; D007700:Kinetics; D013431:Sulfates / Q000494:pharmacology; D013438:Sulfhydryl Compounds / Q000378:metabolism*
chemical_list: D013431:Sulfates; D013438:Sulfhydryl Compounds; C005231:methylmercaptan; D006859:Hydrogen; D004121:Dimethyl Sulfoxide