METHANETHIOL UTILIZATION AND SULFUR REDUCTION BY ANAEROBIC HALOPHILIC SACCHAROLYTIC BACTERIA

A number of sulfur compounds were tested as sulfur sources for the growth of three strains of anaerobic halophilic saccharolytic bacteria isolated from hypersaline water bodies of the eastern Crimea (USSR). Dithionite and sulfite at 1 mM concentration completely inhibited the growth of all strains. Methanethiol turned out to be the sole sulfur source for growth of Halobacteroides strains in the defined medium with glucose and leucine. Methanethiol also stimulated growth of cultures in the complex medium with yeast extract. The Haloincola saccharolytica Z-7787 appeared to be capable of methanethiol formation from methionine. All organisms studied were capable of heterotrophic sulfur reduction, producing up to 13 mM H2S, but no evidence that they gain energy from the process has been obtained. The extremely halophilic Halobacteroides lacunaris may participate in sulfidogenesis at the high salinity (20-30% NaCl). The ecological position of haloanaerobes in halophilic community is discussed.