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 or 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 H2 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
Geobacillus thermoglucosidasius is a thermophilic gram-positive bacterium, and a member of the Bacillota phylum. It was first isolated from soil in Japan in 1983.
Thermoanaerobacter kivui is a thermophilic, anaerobic, nonspore-forming species of bacteria.
Thermacetogenium phaeum is a bacterium, the type species of its genus. It is strictly anaerobic, thermophilic, syntrophic and acetate-oxidizing. Its cells are gram-positive, endospore-forming and rod-shaped. Its type strain is PBT. It has a potential biotechnological role.
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.
Geobacillus jurassicus is a thermophilic bacterium first isolated from a high-temperature petroleum reservoir. It is aerobic, gram-positive, rod-shaped, moderately thermophilic, chemoorganotrophic, and endospore-forming, with type species DS1T.
Caldanaerobacter uzonensis is a thermophilic, anaerobic and heterotrophic bacterium from the genus of Caldanaerobacter which has been isolated from a hot spring in Uzon Caldera in Russia.
Caldanaerobius zeae is a Gram-positive thermophilic, anaerobic, non-spore-forming bacterium from the genus of Caldanaerobius which has been isolated from organic waste leachate in Hoopeston in the United States.
Tepidanaerobacter syntrophicus is an anaerobic, moderately thermophilic and syntrophic bacterium from the genus of Tepidanaerobacter which has been isolated from sewage sludge in Niigata in Japan.
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.
Caldimicrobium rimae is an extremely thermophilic, strictly anaerobic and facultatively chemolithoautotrophic bacterium from the genus of Caldimicrobium which has been isolated from the Treshchinnyi Spring from Uzon Caldera in Russia.
Tepidibacillus infernus is an aerotolerant anaerobic, organotrophic, spore-forming and moderately thermophilic bacterium from the genus of Tepidibacillus which has been isolated from microbial mat from the TauTona Gold Mine in South Africa.
Caldicoprobacter algeriensis is a Gram-positive, thermophilic, anaerobic and non-motile bacterium from the genus of Caldicoprobacter which has been isolated from a hot spring from Guelma in Algeria.
Caldicoprobacter oshimai is a Gram-positive, extremely thermophilic, anaerobic, xylanolytic and non-motile bacterium from the genus of Caldicoprobacter which has been isolated from faeces of sheep from the farm at the University of Georgia in the United States.
Polynucleobacter aenigmaticus is an aerobic, facultatively anaerobic, chemo-organotrophic, non-motile, free-living bacterium of the genus Polynucleobacter.
Thermanaerovibrio acidaminovorans is a moderately thermophilic and anaerobic bacterium from the genus of Thermanaerovibrio which has been isolated from granular methanogenic sludge from Breda in the Netherlands.
Phenylobacterium lituiforme is a moderately thermophilic, facultative anaerobic and motile bacterium from the genus of Phenylobacterium which has been isolated from the Great Artesian Basin from Queensland in Australia.
Nautilia nitratireducens is a Gram-negative thermophilic, chemosynthetic, anaerobic bacterium from the genus of Nautilia which has been isolated from a hydrothermal vent from the East Pacific Rise.
