Production and Fate of Methylated Sulfur Compounds from Methionine and Dimethylsulfoniopropionate in Anoxic Salt Marsh Sediments

Abstract

Anoxic salt marsh sediments were amended with DL-methionine and dimethylsulfoniopropionate (DMSP). Microbial metabolism of methionine yielded methane thiol (MSH) as the major volatile organosulfur product, with the formation of lesser amounts of dimethylsulfide (DMS). Biological transformation of DMSP resulted in the rapid release of DMS and only small amounts of MSH. Experiments with microbial inhibitors indicated that production of MSH from methionine was carried out by procaryotic organisms, probably sulfate-reducing bacteria. Methane-producing bacteria did not metabolize methionine. The involvement of specific groups of organisms in DMSP hydrolysis could not be determined with the inhibitors used, because DMSP was hydrolyzed in all samples except those which were autoclaved. Unamended sediment slurries, prepared from Spartina alterniflora sediments, contained significant (1 to 10 R,M) concentrations of DMS. Endogenous methylated sulfur compounds and those produced from added methionine and DMSP were consumed by sediment microbes. Both sulfate-reducing and methane-producing bacteria were involved in DMS and MSH consumption. Methanogenesis was stimulated by the volatile organosulfur compounds released from methionine and DMSP. However, apparent competition for these compounds exists between methanogens and sulfate reducers. At low (1 ,uM) concentrations of methionine, the terminal S-methyl group was metabolized almost exclusively to CO2 and only small amounts of CH4. At higher (>100 ,IM) concentrations of methionine, the proportion of the methyl-sulfur group converted to CH4 increased. The results of this study demonstrate that methionine and DMSP are potential precursors of methylated sulfur compounds in anoxic sediments and that the microbial community is capable of metabolizing volatile methylated sulfur compounds.

Dimethyl sulfide metabolism in salt marsh sediments

“…Glutaraldehyde was previously shown to inhibit the cleavage of DMSP to DMS in marsh sediments. However, it did not totally eliminate cleavage [43]. Due to this inhibition, the actual rate of DMS production from DMSP in glutaraldehydekilled cores may have been lower than what occurred naturally.…”

“…Howes et al [10] postulated that DMS increases were due to release of the osmolyte DMSP, which is found in Spartina species [20] and its subsequent cleavage to DMS and acrylic acid. Kiene and Visscher [43] have demonstrated that DMSP rapidly yields DMS when added to anoxic marsh sediments. Thus, DMSP from Spartina plants and detritus may be a major source of DMS in marsh sediments.…”

Changes in pore‐water chemistry and methane emission following the invasion of Spartina alterniflora into an oliogohaline marsh

“…DMS is also a suitable substrate for methanogens in marine sediments (Oremland and Polcin 1982;Kiene et al 1986;Giani et al 1996;Lyimo et al 2002), and at high concentrations can be a non-competitive substrate for methanogens (Kiene et al 1986). Kiene (1988) observed that DMS in Spartina sediment slurries contributed to 28% of methane production and 1% or less to dissimilatory sulfate reduction, but at low (1 lM) concentrations, the terminal S-methyl group was metabolized almost exclusively to CO 2 (Kiene and Visscher 1987).…”

Anaerobic oxidation of dimethylsulfide and methanethiol in mangrove sediments is dominated by sulfate-reducing bacteria

“…The sediment was enriched by the addition of dimethylsulfide as the only catabolic substrate and BES as an inhibitor of methanogenic archaea. BES has been used extensively in various ecological studies especially when studying the interaction of sulfate reduction and methanogenesis (Oremland et al, 1982;King, 1984;Kiene & Visscher, 1987;Lomans et al, 1997). However, after several transfers of the enrichment with dimethylsulfide and BES, it was realized that BES was supporting the growth of contaminants.…”

“…In marine systems, they originate mainly from the degradation of dimethylsulfoniopropionate, an osmolyte found in algae and halophilic plant species (e.g. Kiene & Visscher, 1987;Kiene & Taylor, 1988;Kiene, 1990). Emission of volatile organic compounds to the atmosphere is limited because they can be degraded by both aerobic and anaerobic microorganisms.…”