A thermoacidophile is an extremophilic microorganism that is both thermophilic and acidophilic; i.e., it can grow under conditions of high temperature and low pH. The large majority of thermoacidophiles are archaea or bacteria, though occasional eukaryotic examples have been reported. Thermoacidophiles can be found in hot springs and solfataric environments, within deep sea vents, or in other environments of geothermal activity. They also occur in polluted environments, such as in acid mine drainage.
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.
Acidilobales are an order of archaea in the class Thermoprotei.
Acidilobus is a genus of archaea in the family Acidilobaceae.
Aeropyrum is a genus of archaea in the family Desulfurococcaceae.
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
Caldithrix is a genus of thermophilic and anaerobic bacteria, currently assigned to its own phylum.
Methanohalophilus mahii is an obligately anaerobic, methylotrophic, methanogenic cocci-shaped archaeon of the genus Methanohalophilus that can be found in high salinity aquatic environments. The name Methanohalophilus is said to be derived from methanum meaning "methane" in Latin; halo meaning "salt" in Greek; and mahii meaning "of Mah" in Latin, after R.A. Mah, who did substantial amounts of research on aerobic and methanogenic microbes. The proper word in ancient Greek for "salt" is however hals (ἅλς). The specific strain type was designated SLP and is currently the only identified strain of this species.
Thermococcus stetteri is an extremely thermophilic, marine, sulfur-metabolizing archaebacterium. It is anaerobic, its cells being irregular cocci 1 to 2 μm in diameter. Of the strains first isolated, two were motile due to a tuft of flagella, while the other two strains were nonmotile. Its type strain is K-3. It can grow on starch, pectin, and peptides, but not amino acids.
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.
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.
Thermosinus is a Gram-negative bacteria genus from the family of Acidaminococcaceae. Up to now there is only one species of this genus known.
Carboxydocella is a Gram-positive and obligate anaerobe bacterial genus from the family of Syntrophomonadaceae.
Ammonifex is a Gram-negative, extremely thermophilic, strictly anaerobic and motile genus of bacteria from the family of Thermoanaerobacteraceae.
Carboxydothermus is a genus of thermophilic, anaerobic bacteria from the family of Thermoanaerobacteraceae.
Caldimicrobium is a genus of bacteria from the family of Thermodesulfobacteriaceae.
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.
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.
Thermanaerovibrio velox is a Gram-negative, moderately thermophilic, organotrophic and anaerobic bacterium from the genus of Thermanaerovibrio which has been isolated from cyanobacterial mat from Uzon caldera in Russia.
