Pseudomonadota is a major phylum of Gram-negative bacteria. At present, they are considered the predominant phylum within the realm of bacteria. They are naturally found as pathogenic and free-living (non-parasitic) genera. The phylum comprises six classes Acidithiobacilia, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Hydrogenophilia, and Zetaproteobacteria. The Pseudomonadota are widely diverse, with differences in morphology, metabolic processes, relevance to humans, and ecological influence.
The Aquificota phylum is a diverse collection of bacteria that live in harsh environmental settings. The name Aquificota was given to this phylum based on an early genus identified within this group, Aquifex, which is able to produce water by oxidizing hydrogen. They have been found in springs, pools, and oceans. They are autotrophs, and are the primary carbon fixers in their environments. These bacteria are Gram-negative, non-spore-forming rods. They are true bacteria as opposed to the other inhabitants of extreme environments, the Archaea.
The Thermodesulfobacteriota are a phylum of thermophilic sulfate-reducing bacteria.
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.
Halopiger is a genus of archaeans in the family Natrialbaceae that have high tolerance to salinity.
Alviniconcha is a genus of deep water sea snails, marine gastropod mollusks in the family Provannidae. These snails are part of the fauna of the hydrothermal vents in the Indian and Western Pacific Ocean. These and another genus and species within the same family are the only known currently existing animals whose nutrition is derived from an endosymbiotic relationship with a member of bacteria from phylum Campylobacterota and Gammaproteobacteria, occurring as endosymbionts within the vacuoles of Alviniconcha ctenidia. All species of Alviniconcha are thought to be foundational species found near hydrothermal venting fluid supplying their bacterial endosymbionts with vent derived compounds such as hydrogen sulfide. These snails can withstand large variations in temperature, pH, and chemical compositions.
Arcobacter is a genus of Gram-negative, spiral-shaped bacteria in the phylum Campylobacterota. It shows an unusually wide range of habitats, and some species can be human and animal pathogens. Species of the genus Arcobacter are found in both animal and environmental sources, making it unique among the Campylobacterota. This genus currently consists of five species: A. butzleri, A. cryaerophilus, A. skirrowii, A. nitrofigilis, and A. sulfidicus, although several other potential novel species have recently been described from varying environments. Three of these five known species are pathogenic. Members of this genus were first isolated in 1977 from aborted bovine fetuses. They are aerotolerant, Campylobacter-like organisms, previously classified as Campylobacter. The genus Arcobacter, in fact, was created as recently as 1992. Although they are similar to this other genus, Arcobacter species can grow at lower temperatures than Campylobacter, as well as in the air, which Campylobacter cannot.
Deferribacter is a genus in the phylum Deferribacterota (Bacteria).
Nautilia profundicola is a Gram-negative chemolithoautotrophic bacterium found around hydrothermal vents in the deep ocean. It was first discovered in 1999 on the East Pacific Rise at depth of 2,500 metres (8,200 ft), on the surface of the polychaete worm Alvinella pompejana. Nautilia profundicola lives symbiotically on the dorsal hairs of A. pompejana but they may also form biofilms and live independently on the walls of hydrothermal vents. The ability of N. profundicola to survive in an anaerobic environment rich in sulfur, H2 and CO2 of varying temperature makes it a useful organism to study, as these are the conditions that are theorized to have prevailed around the time of the earliest life on earth.
Sulfurimonas is a bacterial genus within the class of Campylobacterota, known for reducing nitrate, oxidizing both sulfur and hydrogen, and containing Group IV hydrogenases. This genus consists of four species: Sulfurimonas autorophica, Sulfurimonas denitrificans, Sulfurimonas gotlandica, and Sulfurimonas paralvinellae. The genus' name is derived from "sulfur" in Latin and "monas" from Greek, together meaning a “sulfur-oxidizing rod”. The size of the bacteria varies between about 1.5-2.5 μm in length and 0.5-1.0 μm in width. Members of the genus Sulfurimonas are found in a variety of different environments which include deep sea-vents, marine sediments, and terrestrial habitats. Their ability to survive in extreme conditions is attributed to multiple copies of one enzyme. Phylogenetic analysis suggests that members of the genus Sulfurimonas have limited dispersal ability and its speciation was affected by geographical isolation rather than hydrothermal composition. Deep ocean currents affect the dispersal of Sulfurimonas spp., influencing its speciation. As shown in the MLSA report of deep-sea hydrothermal vents Campylobacterota, Sulfurimonas has a higher dispersal capability compared with deep sea hydrothermal vent thermophiles, indicating allopatric speciation.
Sulfurovum is a genus within the Campylobacterota which was first described in 2004 with the isolation and description of the type species Sulfurovum lithotrophicum from Okinawa trough hydrothermal sediments. Named for their ability to oxidize sulfur and their egg-like shape, cells are gram-negative, coccoid to short rods. Mesophilic chemolithoautotrophic growth occurs by oxidation of sulfur compounds coupled to the reduction of nitrate or molecular oxygen.
Sulfurovum lithotrophicum is a species of bacteria, the type species of its genus. It is a sulfur-oxidizing chemolithoautotroph within the ε-Proteobacteria isolated from Okinawa Trough hydrothermal sediments. It is mesophilic and also oxidises thiosulfate. It is a gram-negative, non-motile and coccoid to oval-shaped bacterium. The type strain is 42BKTT.
The Nautiliaceae are a family of bacteria placed in an order to itself, Nautiliales, or in the order Campylobacterales. The members of the family are all thermophilic.
Sulfurimonas autotrophica is a sulfur- and thiosulfate-oxidizing bacterium. It is mesophilic, and its cells are short rods, each being motile by means of a single polar flagellum. Its genome has been sequenced.
Sulfurimonas paralvinellae is a hydrogen- and sulfur-oxidizing bacterium. It is a mesophilic chemolithoautotroph.
Deferribacter desulfuricans is a species of sulfur-, nitrate- and arsenate-reducing thermophile first isolated from a deep-sea hydrothermal vent. It is an anaerobic, heterotrophic thermophile with type strain SSM1T.
Lebetimonas is a genus of bacteria from the family Nautiliaceae.
Lebetimonas acidiphila is a thermophilic, acidophilic, hydrogen-oxidizing and motile bacterium from the genus of Lebetimonas. To observe growth there temperature should be between 30 and 68 degrees Celsius.
Nitratiruptor sp. is a genus of deep sea gram-negative Campylobacterota isolated from Iheya North Hydrothermal field in Okinawa Trough (Japan). This rod-shaped microorganism grows chemolithoautotrophically in a wide variety of electron donors and acceptors in absence of light and oxygen. It is also a thermophilic group capable of growing within the range of 37–65 °C with the optimal at 55 °C.
Thioreductor is a Gram-negative, mesophilic, hydrogen-oxidizing, sulfur-reducing and motile genus of bacteria from the phylum Campylobacterota with one known species. Thioreductor micantisoli has been isolated from hydrothermal sediments from the Iheya North from the Mid-Okinawa Trough in Japan.
