Production of methanethiol and dimethyl sulfide by rumen micro-organisms

Abstract

SUMMARYIncubation of rumen fluid for short periods (5 hours) with various sulfur compounds resulted in the accumulation of methanethiol and dimethyl sulfide in the headspace above the fermentation mixture. Suitable substrates included methionine, S-methyl cysteine and dimethylacetothetin among others. Rumen methanethiol appears to arise from direct dethiomethylation of thiomethyl compounds. Some, if not all, of the methionine dethiomethylase activity of rumen fluid requires pyridoxal phosphate as a cofactor. Such a requirement would eliminate the possibility that the dethiomethylation reaction was preceded by deamination as described for certain soil organisms.Benzyl viologen was found to inhibit the production of methane and methanethiol in the presence of methionine and S-methyl cysteine but to have no consistent effect on the production of dimethyl sulfide from these substrates. On the other hand, the dye stimulated the production of methanethiol and dimethyl sulfide from dimethylacetothetin. Carbon tetrachloride e~fectively prevented the formation of dimethyl sulfide but not methanethiol when the sulfur amino acids were used as substrates, but stimulated dimethyl sulfide and methanethiol formation from dimethylacetothetin. Methyl methionine sulfonium chloride gave little or no methanethiol or dimethyl sulfide when incubated with rumei1 fluid. Results are consistent with the concept that rumen methanethiol and dimethyl sulfide can arise from sulfur amino acids that are constituents of the normal ruminant diet.

Thiols in wetland interstitial waters and their role in mercury and methylmercury speciation

“…Microbial pathways for the formation of cysteine, glutathione, and 3-MPA have been well documented in laboratory cultures and in marine sediments (Bird and Moir 1972;Salsbury and Merricks 1975;Kiene and Taylor 1988). Thiols in surface coastal wa- ters have also been attributed to marine phytoplankton (AlFarawati and Van Den Berg 2001;Matrai and Vetter 1988).…”

“…Nanomolar to millimolar levels of thiols have been commonly reported in seawater (Matrai and Vetter 1988;Tang et al 2000a;Al-Farawati and van den Berg 2001) and marine sediment interstitial waters (Luther et al 1986; Kiene and Taylor 1988;MacCrehan and Shea 1995). They can be formed via a variety of pathways, including (1) microbial deamination of sulfur-containing amino acids (Bird and Moir 1972;Salsbury and Merricks 1975;Mopper and Taylor 1986), (2) microbial degradation of dimethylsulfoniopropionate (DMSP) (Shea and MacCrehan 1988) produced by marine algae and halophytic plants (Yoch 2002), and (3) abiotic Michael addition reaction between sulfide or polysulfides and unsaturated organic compounds (Mopper and Taylor 1986;Mopper 1987, 1989). Although their biogeochemical significance in the early diagenesis of organic matter, sulfur (Aizenshtat et al 1995;Boulegue et al 1982), and trace metals such as Cu (Shea and MacCrehan 1988;Leal and Van Den Berg 1998) has been increasingly documented in marine sediments, little is known about the nature, distribution, and biogeochemical roles of thiols in freshwater systems.…”

Inhibitory effects of volatile amines emitted by bacterial culture on the growth of fungi.

“…Volatile substances produced by microorganisms have been studied on soil atmospheres (Banwart and Bremner, 1974), rumen fluids (Salsbury and Merricks, 1975), spoilage meats (Lee et al, 1979), cultures of pathogenic bacteria (Huysmans and Spicer, 1985;Zechman et al, 1986), and cultures of Clostridium (Brooks et al, 1970;Rimbault et al, 1986). However, the effects of these volatile products on other microorganisms have been little known.…”

Objectives and approach

“…H2S was not reported . Cultures of E.coli, Proteus vulgaris, Pseudomonas aeruginosa, Clostridium tetani have been shown to produce methylmercaptan but not H 2S from methionine (Salsbury and Merricks, 1975) . Alternatively from cysteine they can produce H 2S.…”

“…Alternatively from cysteine they can produce H 2S. cysteine (Salsbury and Merricks, 1975) . Relative rates of production for each of the VSCs will depend strongly on the presence of the appropriate strains of bacteria which can utilize them under the prevailing oxygen and substrate concentrations .…”