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Publisher Summary Sulfate-reducing bacteria essentially obtain their energy for growth from the oxidation of a limited number of organic acids, ethanol, or hydogen. The electrons derived from these substrates are used to reduce various sulfur compounds to the level of hydrogen sulfide. Sulfate-reducing bacteria are classified into two genera: (1) desulfotomaculum and (2) desulfovibrio. The former genus contains the spore-forming sulfate reducing bacteria and the thermophilic species. The sulfate-reducing bacteria contain four types of sulfite-reducing enzymes, which can be differentiated on the basis of their spectral properties, substrates, and products. Three of these enzymes appear to reduce bisulfite as their pH optimum is around 6.0; they have been termed bisulfite reductases. The reduction of bisulfite to sulfide occurs by one of two different mechanisms: (1) by direct six-electron reduction of bisulfite to sulfide catalyzed by bisulfite reductase or (2) by three successive two-electron reductions involving three different enzymes |
