Dissimilatory Sulfate or Sulfur Reduction

The sulfur- and sulfate-reducing microorganisms represent a large and diverse group that is strictly anaerobic. Most are eubacteria, but several archaea that reduce sulfur have also been described. 

The analogy between H2O and H2S in oxygenic and anaerobic phototrophy, respectively, was pointed out above. Interestingly, elemental sulfur can be used in respiratory processes. Desul-furomonas acetoxidans grow on acetate, anaerobically reducing stoichiometric amounts of S to H2S  

They occur in anaerobic sediments rich in sulfide and elemental sulfur, and live syntrophically with the phototrophic green sulfur bacteria (Chlorobi-aceae) that photooxidize H2S to S and excrete sulfur extracellularly. Desulfuromonas regenerate H2S by sulfur respiration, using, at least in part, organic matter leaked by Chlombium cells. 

From submarine hydrothermal vent environments, extremely thermophilic anaerobic archaea are capable of sulfur respiration with hydrogen gas  

When obligate anaerobic bacteria carry out dissimilatory sulfate reduction, they are referred to as sulfate reducers or sulfidogens. The traditional sulfate-reducing genera are Desulfovibrio and Desulfotomaculum. Sulfate reduction results in the production of hydrogen sulfide  

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