Sulfate-reducing bacteria

Sulfate-reducing bacteria comprise several groups of bacteria that use sulfate as an oxidizing agent, reducing it to sulfide. Most sulfate-reducing bacteriacan also use other oxidized sulfur compounds such as sulfite and thiosulfate, or elemental sulfur. This type of metabolism is called dissimilatory, since sulfur is not incorporated - assimilated - into any organic compounds. Sulfate-reducing bacteria have been considered as a possible way to deal with acid mine waters that are produced by other bacteria.

Phylogeny
The sulfate-reducing bacteria have been treated as phenotypic group, together with the other sulfur-reducing bacteria, for identification purposes. They are found in several different phylogenetic lines. Three lines are included among the Proteobacteria, all in the delta subgroup:


 * Desulfobacterales
 * Desulfovibrionales
 * Syntrophobacterales

A fourth group including thermophiles is given its own phylum, the Thermodesulfobacteria. The remaining sulfate-reducers are included with other bacteria among the Nitrospirae and the gram-positive Peptococcaceae - for instance Thermodesulfovibrio and Desulfotomaculum, respectively. There is also a single genus of Archaea capable of sulfate reduction, Archaeoglobus.

Environmental markers
The rotten egg odor of hydrogen sulfide is often a marker for the presence of sulfate-reducing bacteria in nature. Sulfate-reducing bacteria are responsible for the sulfurous odors of salt marshes and mud flats, as well as intestinal gas. Sulfate-reducing bacteria slowly degrade tough-to-digest materials that are rich in cellulose in anaerobic environments. Rather than breathing oxygen, they "breathe" sulfate. Sulfate occurs widely in seawater, sediment, or water rich in decaying organic material.