Fermentation of methanethiol and dimethylsulfide by a newly isolated methanogenic bacterium

Abstract

From dilution series in defined mineral medium, a marine iregular 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°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:

$$\begin{array}{*{20}c} {4CH_3 SH + 3H_2 O \to 3CH_4 + HCO_3^ - } \\ { + 4HS^ - + 5H^ + } \\ {(\Delta G^{{\rm O}{\rm I}} = - 36.9kJ/MT)} \\ \end{array} $$

(1)

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 of DMS was accompanied by significant intermediate MT production.