Yellowstone National Park Hot Spring Research Articles

Modification of organosulfur compounds and water-soluble coal-derived material by anaerobic microorganisms

The transformation of organosulfur compounds by anaerobic microorganisms may be of interest for coal desulfurization. An anaerobic microbial community indigenous to cyanobacterial mats of a Yellowstone National Park hot spring was assessed for the ability to evolve volatile sulfur compounds from benzyl methyl sulfide, benzyl methyl disulfide, methionine and water-soluble lignite-derived material. The addition of methionine or benzyl methyl disulfide stimulated the production of methanethiol by slurries made with cyanobacterial mat material. Transformation of methionine appeared to be the direct result of microbial activity. However, the evolution of methanethiol from benzyl methyl disulfide appeared to be the indirect result of microbial activity, that is, the cleavage of the disulfide linkage may have resulted from the reduction by microbially produced hydrogen sulfide. Results indicated a transient interaction of hydrogen sulfide and methanethiol with the coal material. In separate studies, sulfate-reducing bacteria were examined for the modification of water-soluble lignite-derived material. As expected, the sulfur content of the soluble material increased under conditions of sulfate respiration. However, when grown fermentatively without the production of sulfide, two of the nine cultures examined reduced the sulfur content of the soluble material. Most of the cells in all the cultures immediately lysed upon the addition of the soluble material. By 2 weeks, cell densities were greater in cultures amended with soluble coal material than in control cultures.