FERMENTATION OF METHANETHIOL AND DIMETHYLSULFIDE BY A NEWLY ISOLATED METHANOGENIC BACTERIUM

From dilution series in defined mineral medium, a marine irregular coccoid methanogenic bacterium (strain MTP4) was isolated that was able to grow on methanethiol as sole source of energy. The strain also grew on dimethylsulfide, mono-, di-, and trimethylamine, methanol and acetate. On formate the organism produced methane without significant growth. Optimal growth on MT, with doubling times of about 20 h, occurred at 30-degrees-C in marine medium. The isolate required p-aminobenzoate and a further not identified vitamin. Strain MTP4 had a high tolerance to hydrogen sulfide but was very sensitive to mechanical forces or addition of detergents such as Triton X-100 or sodium dodecylsulfate. Methanethiol was fermented by strain MTP4 according to the following equation: 4 CH3SH + 3 H2O --> 3 CH4 + HCO3-+ 4 HS- + 5 H+ (DELTA-G-degrees' = -36.9 kJ/MT) The growth yield was 3.06 g cell dry mass per mol of MT. During growth on MT the isolate released small amounts of DMS and, vice versa, degradation DMS was accompanied by significant intermediate MT production.