Sulfur-reducing bacteria are microorganisms able to reduce elemental sulfur (S0) to hydrogen sulfide (H2S). These microbes use inorganic sulfur compounds as electron acceptors to sustain several activities such as respiration, conserving energy and growth, in absence of oxygen. The final product of these processes, sulfide, has a considerable influence on the chemistry of the environment and, in addition, is used as electron donor for a large variety of microbial metabolisms. Several types of bacteria and many non-methanogenic archaea can reduce sulfur. Microbial sulfur reduction was already shown in early studies, which highlighted the first proof of S0 reduction in a vibrioid bacterium from mud, with sulfur as electron acceptor and H
2 as electron donor. The first pure cultured species of sulfur-reducing bacteria, Desulfuromonas acetoxidans, was discovered in 1976 and described by Pfennig Norbert and Biebel Hanno as an anaerobic sulfur-reducing and acetate-oxidizing bacterium, not able to reduce sulfate. Only few taxa are true sulfur-reducing bacteria, using sulfur reduction as the only or main catabolic reaction. Normally, they couple this reaction with the oxidation of acetate, succinate or other organic compounds. In general, sulfate-reducing bacteria are able to use both sulfate and elemental sulfur as electron acceptors. Thanks to its abundancy and thermodynamic stability, sulfate is the most studied electron acceptor for anaerobic respiration that involves sulfur compounds. Elemental sulfur, however, is very abundant and important, especially in deep-sea hydrothermal vents, hot springs and other extreme environments, making its isolation more difficult. Some bacteria – such as Proteus, Campylobacter, Pseudomonas and Salmonella – have the ability to reduce sulfur, but can also use oxygen and other terminal electron acceptors.
Thermoanaerobacter is a genus in the phylum Bacillota (Bacteria). Members of this genus are thermophilic and anaerobic, several of them were previously described as Clostridium species and members of the now obsolete genera Acetogenium and Thermobacteroides
The family Thermodesulfobiaceae according to the LPSN is located within the order Thermoanaerobacterales and class Clostridia. However, according to the All-Species Living Tree Project it lies outside the clade Bacillota and the genus Caldanaerovirga does not belong to the clade, i.e. Thermodesulfobiaceae is polyphyletic.
Thermoanaerobacter acetoethylicus, formerly called Thermobacteroides acetoethylicus, is a species of thermophilic, nonspore-forming bacteria.
Coprothermobacter proteolyticus, formerly Thermobacteroides proteolyticus, is a thermophilic, non-spore-forming bacteria.
Armatimonas rosea is a Gram-negative bacterium and also the first species to be characterized within the phylum Armatimonadota. The Armatimonadota were previously known as candidate phylum OP10. OP10 was composed solely of environmental 16S rRNA gene clone sequences prior to A. rosea's discovery.
Chthonomonas calidirosea is a Gram-negative bacterium and also the first representative of the new class Chthonomonadetes within the phylum Armatimonadota. The Armatimonadota were previously known as candidate phylum OP10. OP10 was composed solely of environmental 16S rRNA gene clone sequences prior to C. calidirosea's relative, Armatimonas rosea's discovery. It is now known that bacterial communities from geothermal environments, are generally constituted by, at least 5–10% of bacteria belonging to Armatimonadota.
Fimbriimonas ginsengisoli is a Gram-negative bacterium and the first representative of the class Fimbriimonadia within the phylum Armatimonadota. The Armatimonadota were previously known as candidate phylum OP10. OP10 was composed solely of environmental 16S rRNA gene clone sequences prior to F. ginsengisoli's relative, Armatimonas rosea's discovery.
Rhodoferax is a genus of Betaproteobacteria belonging to the purple nonsulfur bacteria. Originally, Rhodoferax species were included in the genus Rhodocyclus as the Rhodocyclus gelatinous-like group. The genus Rhodoferax was first proposed in 1991 to accommodate the taxonomic and phylogenetic discrepancies arising from its inclusion in the genus Rhodocyclus. Rhodoferax currently comprises four described species: R. fermentans, R. antarcticus, R. ferrireducens, and R. saidenbachensis. R. ferrireducens, lacks the typical phototrophic character common to two other Rhodoferax species. This difference has led researchers to propose the creation of a new genus, Albidoferax, to accommodate this divergent species. The genus name was later corrected to Albidiferax. Based on geno- and phenotypical characteristics, A. ferrireducens was reclassified in the genus Rhodoferax in 2014. R. saidenbachensis, a second non-phototrophic species of the genus Rhodoferax was described by Kaden et al. in 2014.
Marinitoga piezophila is a species of rod-shaped, thermo-piezophilic bacteria. It is, anaerobic, chemo-organotrophic, sulfur-reducing, motile, have a mean length of 1-1.5 micrometres and stains Gram-negative. The type strain is KA3T.
Tepidibacter is a genus of Gram-positive bacteria in the family Clostridiaceae.
Acidilobus aceticus is a thermoacidophilic species of anaerobic archaea. The species was originally described in 2000 after being isolated from hot springs in Kamchatka. It is the type species of the genus Acidilobus.
Acidilobus saccharovorans is a thermoacidophilic species of anaerobic archaea. The species was originally described in 2009 after being isolated from hot springs in Kamchatka.
Coprothermobacterota is a phylum of nonmotile, rod-shaped bacteria.
Coprothermobacteria is a taxonomic class of bacteria in the phylum Coprothermobacterota.
Coprothermobacterales is a taxonomic order of thermophilic bacteria in the class Coprothermobacteria of the phylum Coprothermobacterota.
Coprothermobacteraceae is a bacterial family of rod-shaped microorganisms, belonging to the order Coprothermobacterales, class Coprothermobacteria of the phylum Coprothermobacterota.
Coprothermobacter is a genus of rod-shaped microorganisms, belonging to the bacterial family Coprothermobacteraceae of the phylum Coprothermobacterota. This taxonomic genus has been reclassified in 2018, after different phylogenetic studies showed that these bacteria represented a deeply branched taxon of the domain Bacteria; consequently, the clade including this genus has been classified in a separate phylum from Firmicutes, the phylum where it was included before reclassification.
Deferrisoma camini is a moderately thermophilic and anaerobic bacterium from the genus of Deferrisoma which has been isolated from a deep-sea hydrothermal vent from the Eastern Lau Spreading Centre in the Pacific Ocean.
Chloroflexus islandicus is a photosynthetic bacterium isolated from the Strokkur Geyser in Iceland. This organism is thermophilic showing optimal growth at 55°C (131°F) with a pH range of 7.5 – 7.7. C. islandicus grows best photoheterotrophically under anaerobic conditions with light but is capable of chemoheterotrophically growth under aerobic conditions in the dark. C. islandicus has a yellowish green color. The individual cells form unbranched multicellular filaments about 0.6 µm in diameter and 4-7 µm in length.
