Sulfur-reducing bacteria

Sulfur-oxidizing bacteria or Sulfurikanten are autotrophic bacteria, hydrogen sulfide (H2S) and other reduced sulfur compounds, such as thiosulfate ( S2O32 - ), oxidized to elemental sulfur (S) or sulfate. Most can also oxidize elemental sulfur to sulfate. The non- phototrophic ( " colorless " ) sulfur-oxidizing bacteria form a metabolic type, no phylogenetic unit. Many groups are therefore not related and are found in very different taxa.

Sulfur-oxidizing bacteria are sometimes referred to as sulfur bacteria, however, this designation is ambiguous, it is applied to various types of bacterial metabolism.

Two groups of sulfur-oxidizing bacteria physiological be distinguished:

Phototrophic sulfur-oxidizing bacteria - non. These bacteria meet their energy needs by the exergonic oxidation of sulfur. This group includes, for example, Acidithiobacillus thiooxidans ( unicellular, aerobic, acidophilic ), Beggiatoa ( multicellular, ply, aerobic, non- acidophilic ), many endolithisch living bacteria and in 1999 discovered Thiomargarita namibiensis, the " sulfur pearl of Namibia ", which with a diameter of up to three quarters of a millimeter largest bacterium already visible with the naked eye.

Photoautotrophic sulfur-oxidizing bacteria. These bacteria possess bacteriochlorophyll and use hydrogen sulfide ( H2S) or other reduced sulfur compounds as electron source ( reductant ) for anoxygenic photosynthesis. This group includes the obligate anaerobic "green sulfur bacteria" ( as the genus Chlorobium ) and also obligate anaerobic " purple sulfur bacteria" ( as the genus Chromatium ).

Cyanobacteria operate an oxygenic photosynthesis. They therefore have two photosystems and can use water as an electron source for the reduction of carbon dioxide ( to form elemental oxygen). Some cyanobacteria can but in the presence of hydrogen sulfide also use this as a source of electrons ( to form elemental sulfur) and in this case use only photosystem I, then run a anoxygenic photosynthesis. Accordingly, they can be attributed to the second group, the photoautotrophic sulfur bacteria. It indicates the ability to use hydrogen sulfide as reductant as a relic of the evolution of photosynthesis oxygener from the anoxygenic.