Campylobacteria | |
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Campylobacter jejuni bacteria | |
Scientific classification | |
Domain: | Bacteria |
Phylum: | Campylobacterota |
Class: | "Campylobacteria" Waite et al. 2017 |
Orders | |
Synonyms | |
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The Campylobacteria are a class of Gram-negative bacteria. It used to be known as Epsilonproteobacteria. [1] [a] Only a few genera have been characterized, including the curved to spirilloid Wolinella , Helicobacter , and Campylobacter .
Most of the known species inhabit the digestive tracts of animals and serve as symbionts (Wolinella spp. in cattle) or pathogens (Helicobacter spp. in the stomach, Campylobacter spp. in the duodenum). However, numerous environmental sequences and isolates of Campylobacteria have been recovered from hydrothermal vents and cold seep habitats. Examples of isolates include Sulfurimonas autotrophica, [3] Sulfurimonas paralvinellae, [4] Sulfurovum lithotrophicum [5] and Nautilia profundicola . [6] A member of the phylum Campylobacterota occurs as an endosymbiont in the large gills of the deepwater sea snail Alviniconcha hessleri . [7]
Many Campylobacteria are motile with flagella. [8] The Campylobacteria found at deep-sea hydrothermal vents characteristically exhibit chemolithotrophy, meeting their energy needs by oxidizing reduced sulfur, formate, or hydrogen coupled to the reduction of nitrate or oxygen. [9] Autotrophic Campylobacteria use the reverse Krebs cycle to fix carbon dioxide into biomass, a pathway originally thought to be of little environmental significance. The oxygen sensitivity of this pathway is consistent with their microaerophilic or anaerobic niche in these environments, and their likely evolution in the Mesoproterozoic oceans, [10] which are thought to have been sulfidic with low levels of oxygen available from cyanobacterial photosynthesis. [11]
Pseudomonadota is a major phylum of Gram-negative bacteria. Currently, 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 Acidithiobacillia, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Hydrogenophilia, and Zetaproteobacteria. The Pseudomonadota are widely diverse, with differences in morphology, metabolic processes, relevance to humans, and ecological influence.
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.
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.
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.
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.
Palaeococcus ferrophilus is a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney. It cells are irregular cocci and motile with multiple polar flagella.
Methylocella tundrae is a species of bacterium. It is notable for oxidising methane. Its cells are aerobic, Gram-negative, non-motile, dinitrogen-fixing rods. Strain T4T is the type strain.
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.
Persephonella guaymasensis is a thermophilic, hydrogen-oxidizing microaerophile first isolated from a deep-sea hydrothermal vent. It is strictly chemolithoautotrophic, microaerophilic, motile, 2-4 micrometres in size, rod-shaped, Gram-negative and non-sporulating. Its type strain is EX-H2T.
Nautilia lithotrophica is a thermophilic sulfur-reducing epsilon-proteobacterium isolated from a deep-sea hydrothermal vent. It is strictly anaerobic, with type strain 525T.
Sulfuricurvum kujiense is a facultatively anaerobic, chemolithoautotrophic, sulfur-oxidizing bacterium, the type species of its genus. Its cells are motile, curved rods and have a single polar flagellum. Its type strain is YK-1T.
Caminibacter profundus is a species of moderately thermophilic, microaerobic to anaerobic, chemolithoautotrophic bacterium. It is a Gram-negative, non-motile rod, with type strain CRT.
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, the temperature should be between 30 and 68 degrees Celsius.
Nautilia abyssi is a thermophilic, sulfur-reducing and strictly anaerobic bacterium from the genus of Nautilia which has been isolated from a hydrothermal chimney from the East Pacific Rise.
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.