A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, with an optimum growth range from 20 to 45 °C. The optimum growth temperature for these organisms is 37 °C. The term is mainly applied to microorganisms. Organisms that prefer extreme environments are known as extremophiles. Mesophiles have diverse classifications, belonging to two domains: Bacteria, Archaea, and to kingdom Fungi of domain Eucarya. Mesophiles belonging to the domain Bacteria can either be gram-positive or gram-negative. Oxygen requirements for mesophiles can be aerobic or anaerobic. There are three basic shapes of mesophiles: coccus, bacillus, and spiral.
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
Thermoanaerobacter ethanolicus is a species of thermophilic, anaerobic, non-spore-forming bacteria.
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.
Thermoanaerobacter brockii, formerly Thermoanaerobium brockii, is a thermophilic, anaerobic, spore-forming bacterium.
Thermoanaerobacter italicus is a species of thermophilic, anaerobic, spore-forming bacteria.
Thermoanaerobacter kivui is a thermophilic, anaerobic, nonspore-forming species of bacteria.
Thermoanaerobacter pseudethanolicus is a thermophilic, strictly anaerobic, spore-forming bacteria that was first found at Yellowstone National Park in the United States. Because of its ability to efficiently ferment sugars, it is thought to be of potential use in producing industrial alcohol.
Fervidobacterium gondwanense is a species of thermophilic anaerobic bacteria. It is non-sporulating, motile, gram-negative, and rod-shaped. F. godwanense was isolated in Great Artesian basin in Australia from non-volcanicly heated geothermal waters.
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.
Fervidobacterium islandicum is a species of extremely thermophilic anaerobic bacteria, first isolated from an Icelandic hot spring.
Bifidobacterium thermacidophilum is a Gram-positive, rod-shaped species of bacteria. Strains of this species were originally isolated from an anaerobic digester used to treat wastewater from a tofu farm. The species is thermophilic and can grow at a temperature of 49.5 °C.
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.
Caldanaerobacter is a Gram-positive or negative and strictly anaerobic genus of bacteria from the family of Thermoanaerobacteraceae.
Anaerolineaceae is a family of bacteria from the order of Anaerolineales. Anaerolineaceae bacteria occur in marine sediments. There are a total of twelve genera in this family, most of which only encompass one species. All known members of the family are Gram-negative and non-motile. They also do not form bacterial spores and are either mesophilic or thermophilic obligate anaerobes. It is also known that all species in this family are chemoheterotrophs.
Coprothermobacterota is a phylum of nonmotile, rod-shaped bacteria.
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.
