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.
Geoglobus is a hyperthermophilic member of the Archaeoglobaceae within the Euryarchaeota. It consists of two species, the first, G. ahangari, isolated from the Guaymas Basin hydrothermal system located deep within the Gulf of California. As a hyperthermophile, it grows best at a temperature of 88 °C and cannot grow at temperatures below 65 °C or above 90 °C. It possess an S-layer cell wall and a single flagellum. G. ahangari is an anaerobe, using poorly soluble ferric iron (Fe3+) as a terminal electron acceptor. It can grow either autotrophically using hydrogen gas (H2) or heterotrophically using a large number of organic compounds, including several types of fatty acids, as energy sources. G. ahangari was the first archaeon isolated capable of using hydrogen gas coupled to iron reduction as an energy source and the first anaerobe isolated capable of using long-chain fatty acids as an energy source.
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
Deferribacter is a genus in the phylum Deferribacterota (Bacteria).
Caldithrix is a genus of thermophilic and anaerobic bacteria, currently assigned to its own phylum.
Deferribacter autotrophicus is the most recently discovered species in the Deferribacter genus, isolated from a deep sea hydrothermal field. This motile, thermophilic, anaerobic organism stands out for its unique metabolic versatility, particularly its autotrophic capabilities which had not been previously observed in its genus.
Thermoanaerobacter siderophilus is a dissimilatory Fe(III)-reducing, anaerobic, thermophilic bacterium that was firstly isolated from the sediment of a hydrothermal vent found near the Karymsky volcano, in the Kamchatka peninsula, Russia. It is spore-forming, with type strain SR4T.
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.
Moorella humiferrea is a Gram-positive thermophilic, anaerobic and endospore-forming bacterium from the genus Moorella, which has been isolated from sediments from the Grot geyser, Valley of Geysers, Kamchatka, Russia. This microorganism is able to grow and reduce iron(III) oxide when small amounts of humic acid are available.
Caldanaerobius is a moderately thermophilic and anaerobic genus of bacteria from the family of Thermoanaerobacteraceae with one known species.
Hippea is an obligate anaerobic and moderately thermophilic bacteria genus from the family of Desulfobacteraceae. Hippea is named after the German microbiologist Hans Hippe.
Hippea alviniae is a thermoacidophilic and obligately anaerobic bacterium from the genus of Hippea which has been isolated from a hydrothermal vent from the East Pacific Rise.
Tepidibacillus is a genus of bacteria from the family of Bacillaceae.
Tepidibacillus fermentans is a Gram-positive, moderately thermophilic, spore-forming and motile bacterium from the genus of Tepidibacillus which has been isolated from an underground gas storage in Severo-Stavropolskoye in Russia.
Vulcanibacillus is a genus of bacteria from the family of Bacillaceae with one known species. Vulcanibacillus modesticaldus has been isolated from a hydrothermal vent from the Rainbow Vent Field.
Thermostilla is a thermophilic genus of bacteria from the family of Planctomycetaceae with one known species. Thermostilla marina has been isolated from a hydrothermal vent from a Vulcano Island in Italy.
Deferrisoma palaeochoriense is a thermophilic, anaerobic and mixotrophic bacterium from the genus of Deferrisoma which has been isolated from a hydrothermal vent from the Palaeochori Bay from Greece.
Inmirania is a thermophilic and facultatively autotrophic genus of bacteria from the family of Ectothiorhodospiraceae with one known species. Inmirania thermothiophila has been isolated from water and sediments from a thermal spring from the Kuril Islands.
Thermodesulfobacterium hveragerdense is a bacterial species belonging to genus Thermodesulfobacterium, which are thermophilic sulfate-reducing bacteria. This species is found in aquatic areas of high temperature, and lives in freshwater like most, but not all Thermodesulfobacterium species It was first isolated from hotsprings in Iceland.
