FORMATION OF METHYLMERCAPTAN AND DIMETHYLSULFIDE FROM METHOXYLATED AROMATIC-COMPOUNDS IN ANOXIC MARINE AND FRESH-WATER SEDIMENTS

Anaerobic formation of dimethylsulfide (DMS) and methylmercaptan (MSH) in anoxic sulfide-containing slurries from marine and fresh water sediments was stimulated by addition of syringae (4-hydroxy,3,5,-dimethyoxybenzoate) and 3,4,5,-tri-methoxybenzoate. The release of DMS and MSH occurred during the consumption of the aromatic monomers and ceased after their depletion. DMS was the dominant methylated sulfur compound in fresh water sediments, in contrast to marine sediments where MSH was predominant. No production of volatile organic sulfur compounds was observed in slurries containing gallate (3,4,5,-tri-hydroxybenzoate) or in autoclaved controls. About 50-60% of the methoxy carbon could be accounted for by peak accumulation of DMS and MSH. In the saline sediments, large amounts of CH4 were formed during the period when DMS and MSH disappeared. About 65-70% of the methylcarbon of the volatile methylated sulfur compounds (VMSC) could be accounted for in the produced CH4. This study demonstrates a previously unknown microbial process by which DMS and MSH are formed during anaerobic decomposition of methoxylated aromatic compounds in marine and freshwater sediments.