The Rhizobiales are an order of Gram-negative Alphaproteobacteria. The rhizobia, which fix nitrogen and are symbiotic with plant roots, appear in several different families; the four families Bradyrhizobiaceae, Hyphomicrobiaceae, Phyllobacteriaceae, Rhizobiaceae contain at least six genera of nitrogen-fixing, legume-nodulating, microsymbiotic bacteria. Examples are Rhizobium. Species of the Methylocystaceae are methanotrophs. Other important genera are the human pathogens Brucella, as well as Agrobacterium. Bartonellaceae Gieszczykiewicz 1939 emend. Brenner et al. 1993 Beijerinckiaceae Garrity et al. 2006 Bradyrhizobiaceae Garrity et al. 2006 Brucellaceae Breed et al. 1957 Cohaesibacteraceae Hwang and Cho 2008 emend. Gallego et al. 2010 Mabikibacteraceae Choi et al. 2017 Hyphomicrobiaceae Babudieri 1950 Methylobacteriaceae Garrity et al. 2006 Methylocystaceae Bowman 2006 Phyllobacteriaceae Mergaert and Swings 2006 Rhizobiaceae Conn 1938 Rhodobiaceae Garrity et al. 2006 Roseiarcaceae Kulichevskaya et al. 2014 Xanthobacteraceae Lee et al. 2005 These families have been proposed but not yet validly published according to the rules of the Bacteriological Code.
"Aurantimonadaceae" Denner et al. 2003 "Devosiaceae" Yarza et al. 2014 "Kaistiaceae" Yarza et al. 2014 "Labriaceae" Beck et al. 2015 "Lutibaculaceae" Yarza et al. 2014 "Methyloligellaceae" Yarza et al. 2014 "Methylopilaceae" Beck et al. 2015 "Pleomorphomonadaceae" Yarza et al. 2014 "Rhodomicrobiaceae" Yarza et al. 2014 "Stappiaceae" Yarza et al. 2014 "Thermopetrobacteraceae" Yarza et al. 2014 The following genera belong to the Rhizobiales but have not been assigned to a family. Alsobacter Bao et al. 2014 Amorphus Zeevi Ben Yosef et al. 2008 Bauldia Yee et al. 2010 Methylobrevis Poroshina et al. 2015 Methyloceanibacter Takeuchi et al. 2014 Methyloligella Doronina et al. 2014 Vasilyevaea Yee et al. 2010 The accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature and National Center for Biotechnology Information and the phylogeny is based on whole-genome sequences. Natural genetic transformation has been reported in at least three Rhizobiales species: Agrobacterium tumefaciens, Methylobacterium organophilum, Bradyrhizobium japonicum.
Natural genetic transformation is a sexual process involving DNA transfer from one bacterial cell to another through the intervening medium, the integration of the donor sequence into the recipient genome by homologous recombination. Lar1 Kuykendall, L. D. and Dazzo, F. B. 2005. Allorhizobium. In Brenner, Krieg and Garrity, The Alpha-, Beta-, Delta- and Epsilonproteobacteria, The Proteobacteria, Part C, Bergey’s Manual of Systematic Bacteriology, 2nd. Ed. Vol. 2, New York, NY, pp. 345–346. Kuykendall, L. D. 2005 Genus Azorhizobium. In Brenner, Krieg and Garrity, The Alpha-, Beta-, Delta- and Epsilonproteobacteria, The Proteobacteria, Part C, Bergey’s Manual of Systematic Bacteriology, 2nd. Ed. Vol. 2, New York, NY, pp. 505–506. Kuykendall, L. D. 2005. Genus Bradyrhizobium, family Bradyrhizobiaceae. In: Bergey's Manual of Systematic Bacteriology, 2nd Edition, 2nd Volume. George Garrity, Springer–Verlag, New York, NY, pp. 438–443. Chen, W. X. E. T. Wang, L. D. Kuykendall. 2005. Genus Mesorhizobium, Family Photobacteriaceae.
In: Bergey's Manual of Systematic Bacteriology, 2nd Edition, 2nd Volume. George Garrity, Springer–Verlag, New York, NY, pp. 403–408. Kuykendall, L. D. J. M. Young, E. Martínez-Romero, A. Kerr, H. Sawada. 2005. Genus Rhizobium, a divergent genus in a revised family, the Rhizobiaceae. In: Bergey's Manual of Systematic Bacteriology, 2nd Edition, 2nd Volume. George Garrity, Springer–Verlag, New York, NY, pp. 324–340
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the gram-staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane. Gram-negative bacteria are found everywhere, in all environments on Earth that support life; the gram-negative bacteria include the model organism Escherichia coli, as well as many pathogenic bacteria, such as Pseudomonas aeruginosa, Neisseria gonorrhoeae, Chlamydia trachomatis, Yersinia pestis. They are an important medical challenge, as their outer membrane protects them from many antibiotics. Additionally, the outer leaflet of this membrane comprises a complex lipopolysaccharide whose lipid A component can cause a toxic reaction when these bacteria are lysed by immune cells; this toxic reaction can include fever, an increased respiratory rate, low blood pressure — a life-threatening condition known as septic shock.
Several classes of antibiotics have been designed to target gram-negative bacteria, including aminopenicillins, ureidopenicillins, beta-lactam-betalactamase combinations, Folate antagonists and carbapenems. Many of these antibiotics cover gram positive organisms; the drugs that target gram negative organisms include aminoglycosides and Ciprofloxacin. Gram-negative bacteria display these characteristics: An inner cell membrane is present A thin peptidoglycan layer is present Has outer membrane containing lipopolysaccharides in its outer leaflet and phospholipids in the inner leaflet Porins exist in the outer membrane, which act like pores for particular molecules Between the outer membrane and the cytoplasmic membrane there is a space filled with a concentrated gel-like substance called periplasm The S-layer is directly attached to the outer membrane rather than to the peptidoglycan If present, flagella have four supporting rings instead of two Teichoic acids or lipoteichoic acids are absent Lipoproteins are attached to the polysaccharide backbone Some contain Braun's lipoprotein, which serves as a link between the outer membrane and the peptidoglycan chain by a covalent bond Most, with few exceptions, do not form spores Along with cell shape, gram-staining is a rapid diagnostic tool and once was used to group species at the subdivision of Bacteria.
The kingdom Monera was divided into four divisions based on gram-staining: Firmacutes, Gracillicutes and Mendocutes. Since 1987, the monophyly of the gram-negative bacteria has been disproven with molecular studies; however some authors, such as Cavalier-Smith still treat them as a monophyletic taxon and refer to the group as a subkingdom "Negibacteria". Bacteria are traditionally classified based on their gram-staining response into the gram-positive and gram-negative groups, it was traditionally thought that the groups represent lineages, i.e. the extra membrane only evoved once, such that gram-negative bacteria are more related to one another than to any gram-positive bacteria. While this is true, the classification system breaks down in some cases, with lineage groupings not matching the staining result. Thus, gram-staining cannot be reliably used to assess familial relationships of bacteria. Staining gives reliable information about the composition of the cell membrane, distinguishing between the presence or absence of an outer lipid membrane.
Of these two structurally distinct groups of prokaryotic organisms, monoderm prokaryotes are thought to be ancestral. Based upon a number of different observations including that the gram-positive bacteria are the major reactors to antibiotics and that gram-negative bacteria are, in general, resistant to them, it has been proposed that the outer cell membrane in gram-negative bacteria evolved as a protective mechanism against antibiotic selection pressure; some bacteria such as Deinococcus, which stain gram-positive due to the presence of a thick peptidoglycan layer, but possess an outer cell membrane are suggested as intermediates in the transition between monoderm and diderm bacteria. The diderm bacteria can be further differentiated between simple diderms lacking lipopolysaccharide; the conventional LPS-diderm group of gram-negative bacteria are uniquely identified by a few conserved signature indel in the HSP60 protein. In addition, a number of bacterial taxa that are either part of the phylum Firmicutes or branches in its proximity are found to possess a diderm cell structure.
They lack the GroEL signature. The presence of this CSI in all se
Terrabacteria is a taxon containing two-thirds of prokaryote species, including those in the gram positive phyla as well as the phyla Cyanobacteria and Deinococcus-Thermus. It derives its name from the evolutionary pressures of life on land. Terrabacteria possess important adaptations such as resistance to environmental hazards and oxygenic photosynthesis; the unique properties of the cell wall in gram-positive taxa, which evolved in response to terrestrial conditions, have contributed toward pathogenicity in many species. These results now leave open the possibility that terrestrial adaptations may have played a larger role in prokaryote evolution than understood. Terrabacteria was proposed in 2004 for Actinobacteria and Deinococccus-Thermus and was expanded to include Firmicutes and Chloroflexi. Other phylogenetic analyses have supported the close relationships of these phyla. Most species of prokaryotes not placed in Terrabacteria were assigned to the taxon Hydrobacteria, in reference to the moist environment inferred for the common ancestor of those species.
Terrabacteria and Hydrobacteria were inferred to have diverged 3 billion years ago, suggesting that land had been colonized by prokaryotes at that time. Together and Hydrobacteria form a large group containing 99% of all Eubacteria, placed in the taxon Selabacteria, in allusion to their phototrophic abilities. Terrabacteria should not be confused with the described taxon "Glidobacteria", which includes only some members of Terrabacteria but excludes Firmicutes and Actinobacteria, is not supported by molecular phylogenetic data. Tree from
Betaproteobacteria are a class of gram-negative bacteria, one of the eight classes of the phylum Proteobacteria. The Betaproteobacteria are a class comprising over 400 species of bacteria. Together, the Betaproteobacteria represent a broad variety of metabolic strategies and occupy diverse environments from obligate pathogens living within host organisms to oligotrophic groundwater ecosystems. Whilst most members of the Betaproteobacteria are heterotrophic, deriving both their carbon and electrons from organocarbon sources, some are photoheterotrophic, deriving energy from light and carbon from organocarbon sources. Other genera are autotrophic, deriving their carbon from bicarbonate or carbon dioxide and their electrons from reduced inorganic ions such as nitrite, thiosulfate or sulfide - many of these chemolithoautotrophic Betaproteobacteria are economically important, with roles in maintaining soil pH and in elementary cycling. Other economically important members of the Betaproteobacteria are able to use nitrate as their terminal electron acceptor and can be used industrially to remove nitrate from wastewater by denitrification.
A number of Betaproteobacteria are diazotrophs, meaning that they can fix molecular nitrogen from the air as their nitrogen source for growth - this is important to the farming industry as it is a primary means of ammonium levels in soils rising without the presence of leguminous plants. The Betaproteobacteria are one of the eight classes that make up the "Proteobacteria"; the Betaproteobacteria are most related to the Gammaproteobacteria, Acidithiobacillia and Hydrogenophilalia, together they make up a taxon, called "Chromatibacteria". Four orders of Betaproteobacteria are recognised - the Burkholderiales, the Neisseriales, the Nitrosomonadales and the Rhodocyclales; the name "Procabacteriales" was proposed for an order of endosymbionts of Acanthamoeba, but since they cannot be grown in culture and studies have been limited, the name has never been validly or published, thus is no more than a nickname without any standing in nomenclature. An extensive reclassification of families and orders of the class based on a polyphasic analysis was published in 2017, that removed the order Hydrogenophilales from the class and into a novel class of the "Proteobacteria", the Hydrogenophilalia.
The same study merged the former order Methylophilales into the Nitrosomonadales. The four orders of the Betaproteobactera are sub-divided into families:Burkholderiales comprises the families Burkholderiacae, Commamonadaceae and Sutterellaceae; the order Burkholderiales comprises a range of morphologies, including rods, curved rods, cocci and multicellular'tablets'. Both heterotrophs and photoheterotrophs are found along with some facultative autotrophs. Neisseriales comprises the families Chromobacteriaceae; the order Neisseriales comprises morphologies including cocci, curved rods, rods, multicellular ribbons and filaments. Most organisms are heterotrophs with some facultative chemolithoheterotrophs. Nitrosomonadales comprises the families Nitrosomonadaceae, Thiobacillaceae, Sterolibacteriacae and Gallionellaceae; the order comprises morphologies including rods and curved rods. Most organisms are chemolithoautotrophs with some methylotrophs and heterotrophs Rhodocyclales comprises the families Rhodocyclaceae and Zoogloeaceae.
Morphologies include rods, curved rods, rings and cocci. Most species in this order are heterotrophs with some chemolithoautotrophs; some members of the Betaproteobacteria can cause disease in various eukaryotic organisms, including in humans, such as members of the genus Neisseria: N. gonorrhoeae and N. meninngitides being primary examples, which cause gonorrhea and meningitis as well as Bordetella pertussis which causes whooping cough. Other members of the class can infect plants, such as Burkholderia cepacia which causes bulb rot in onions as well as Xylophilus ampelinus which causes necrosis of grapevines. Various human activities, such as fertilizer production and chemical plant usage, release significant amounts of ammonium ions into rivers and oceans. Ammonium buildup in aquatic environments is dangerous because high ammonium content can lead to eutrophication. Biological wastewater treatment systems, as well as other biological ammonium-removing methods, depend on the metabolism of various Bacteria including members of the Nitrosomonadales of the Betaproteobacteria that undergo nitrification and a wide range of organisms capable of denitrification to remove excessive ammonia from wastewater by first oxidation into nitrate and nitrite and reduction into molecular nitrogen gas, which leaves the ecosystem and is carried into the atmosphere.
Gammaproteobacteria Hydrogenophilalia Acidithiobacillia Betaproteobacteria at the US National Library of Medicine Medical Subject Headings
Bacteria are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. A few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, are present in most of its habitats. Bacteria inhabit soil, acidic hot springs, radioactive waste, the deep portions of Earth's crust. Bacteria live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, only about half of the bacterial phyla have species that can be grown in the laboratory; the study of bacteria is known as a branch of microbiology. There are 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water. There are 5×1030 bacteria on Earth, forming a biomass which exceeds that of all plants and animals. Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere.
The nutrient cycle includes the decomposition of dead bodies. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Data reported by researchers in October 2012 and published in March 2013 suggested that bacteria thrive in the Mariana Trench, with a depth of up to 11 kilometres, is the deepest known part of the oceans. Other researchers reported related studies that microbes thrive inside rocks up to 580 metres below the sea floor under 2.6 kilometres of ocean off the coast of the northwestern United States. According to one of the researchers, "You can find microbes everywhere—they're adaptable to conditions, survive wherever they are."The famous notion that bacterial cells in the human body outnumber human cells by a factor of 10:1 has been debunked. There are 39 trillion bacterial cells in the human microbiota as personified by a "reference" 70 kg male 170 cm tall, whereas there are 30 trillion human cells in the body.
This means that although they do have the upper hand in actual numbers, it is only by 30%, not 900%. The largest number exist in the gut flora, a large number on the skin; the vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, though many are beneficial in the gut flora. However several species of bacteria are pathogenic and cause infectious diseases, including cholera, anthrax and bubonic plague; the most common fatal bacterial diseases are respiratory infections, with tuberculosis alone killing about 2 million people per year in sub-Saharan Africa. In developed countries, antibiotics are used to treat bacterial infections and are used in farming, making antibiotic resistance a growing problem. In industry, bacteria are important in sewage treatment and the breakdown of oil spills, the production of cheese and yogurt through fermentation, the recovery of gold, palladium and other metals in the mining sector, as well as in biotechnology, the manufacture of antibiotics and other chemicals.
Once regarded as plants constituting the class Schizomycetes, bacteria are now classified as prokaryotes. Unlike cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and harbour membrane-bound organelles. Although the term bacteria traditionally included all prokaryotes, the scientific classification changed after the discovery in the 1990s that prokaryotes consist of two different groups of organisms that evolved from an ancient common ancestor; these evolutionary domains are called Archaea. The word bacteria is the plural of the New Latin bacterium, the latinisation of the Greek βακτήριον, the diminutive of βακτηρία, meaning "staff, cane", because the first ones to be discovered were rod-shaped; the ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, about 4 billion years ago. For about 3 billion years, most organisms were microscopic, bacteria and archaea were the dominant forms of life. Although bacterial fossils exist, such as stromatolites, their lack of distinctive morphology prevents them from being used to examine the history of bacterial evolution, or to date the time of origin of a particular bacterial species.
However, gene sequences can be used to reconstruct the bacterial phylogeny, these studies indicate that bacteria diverged first from the archaeal/eukaryotic lineage. The most recent common ancestor of bacteria and archaea was a hyperthermophile that lived about 2.5 billion–3.2 billion years ago. Bacteria were involved in the second great evolutionary divergence, that of the archaea and eukaryotes. Here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves related to the Archaea; this involved the engulfment by proto-eukaryotic cells of alphaproteobacterial symbionts to form either mitochondria or hydrogenosomes, which are still found in all known Eukarya. Some eukaryotes that contained mitochondria engulfed cyanobacteria-like organisms, leading to the formation of chloroplasts in algae and plants; this is known as primary endosymbiosis. Bacteria display a wide diversity of sizes, called morphologies.
Bacterial cells are about one-tenth the size of eukaryotic cells
Streptococcus is a genus of gram-positive coccus or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales, in the phylum Firmicutes. Cell division in streptococci occurs along a single axis, so as they grow, they tend to form pairs or chains that may appear bent or twisted; the term was coined in 1877 by Viennese surgeon Albert Theodor Billroth, by combining the prefix "strepto-", together with the suffix "-coccus" Most streptococci are oxidase-negative and catalase-negative, many are facultative anaerobes. In 1984, many bacteria grouped in the genus Streptococcus were separated out into the genera Enterococcus and Lactococcus. Over 50 species are recognised in this genus; this genus has been found to be part of the salivary microbiome. In addition to streptococcal pharyngitis, certain Streptococcus species are responsible for many cases of pink eye, bacterial pneumonia, endocarditis and necrotizing fasciitis. However, many streptococcal species are not pathogenic, form part of the commensal human microbiota of the mouth, skin and upper respiratory tract.
Streptococci are a necessary ingredient in producing Emmentaler cheese. Species of Streptococcus are classified based on their hemolytic properties. Alpha-hemolytic species cause oxidization of iron in hemoglobin molecules within red blood cells, giving it a greenish color on blood agar. Beta-hemolytic species cause complete rupture of red blood cells. On blood agar, this appears. Gamma-hemolytic species cause no hemolysis. Beta-hemolytic streptococci are further classified by Lancefield grouping, a serotype classification; the 20 described serotypes are named Lancefield groups A to V. This system of classification was developed by Rebecca Lancefield, a scientist at Rockefeller University. In the medical setting, the most important groups are the alpha-hemolytic streptococci S. pneumoniae and Streptococcus viridans group, the beta-hemolytic streptococci of Lancefield groups A and B. Table: Medically relevant streptococci When alpha-hemolysis is present, the agar under the colony will appear dark and greenish due to the conversion of hemoglobin to green biliverdin.
Streptococcus pneumoniae and a group of oral streptococci display alpha-hemolysis. Alpha-hemolysis is termed incomplete hemolysis or partial hemolysis because the cell membranes of the red blood cells are left intact; this is sometimes called green hemolysis because of the color change in the agar. S. pneumoniae, is a leading cause of bacterial pneumonia and occasional etiology of otitis media, sinusitis and peritonitis. Inflammation is thought to be the major cause of how pneumococci cause disease, hence the tendency of diagnoses associated with them to involve inflammation; the viridans streptococci are a large group of commensal bacteria that are either alpha-hemolytic, producing a green coloration on blood agar plates, or nonhemolytic. They possess no Lancefield antigens. Beta hemolysis, sometimes called complete hemolysis, is a complete lysis of red cells in the media around and under the colonies: the area appears lightened and transparent. Streptolysin, an exotoxin, is the enzyme produced by the bacteria which causes the complete lysis of red blood cells.
There are two types of streptolysin: Streptolysin O and streptolysin S. Streptolysin O is an oxygen-sensitive cytotoxin, secreted by most group A Streptococcus, interacts with cholesterol in the membrane of eukaryotic cells, results in beta-hemolysis under the surface of blood agar. Streptolysin S is an oxygen-stable cytotoxin produced by most GAS strains which results in clearing on the surface of blood agar. SLS affects immune cells, including polymorphonuclear leukocytes and lymphocytes, is thought to prevent the host immune system from clearing infection. Streptococcus pyogenes, or GAS, displays beta hemolysis; some weakly beta-hemolytic species cause intense hemolysis when grown together with a strain of Staphylococcus. This is called the CAMP test. Streptococcus agalactiae displays this property. Clostridium perfringens can be identified presumptively with this test. Listeria monocytogenes is positive on sheep's blood agar. Group A S. pyogenes is the causative agent in a wide range of group A streptococcal infections.
These infections may be invasive. The noninvasive infections tend to be less severe; the most common of these infections include impetigo. Scarlet fever is a noninvasive infection, but has not been as common in recent years; the invasive infections caused by group A beta-hemolytic streptococci tend to be more severe and less common. This occurs when the bacterium is able to infect areas where it is not found, such as the blood and the organs; the diseases that may
A thermophile is an organism—a type of extremophile—that thrives at high temperatures, between 41 and 122 °C. Many thermophiles are archaea. Thermophilic eubacteria are suggested to have been among the earliest bacteria. Thermophiles are found in various geothermally heated regions of the Earth, such as hot springs like those in Yellowstone National Park and deep sea hydrothermal vents, as well as decaying plant matter, such as peat bogs and compost. Thermophiles can survive at high temperatures, whereas other bacteria would be damaged and sometimes killed if exposed to the same temperatures; the enzymes in thermophiles function at high temperatures. Some of these enzymes are used in molecular biology, for example, heat-stable DNA polymerases for PCR), in washing agents. "Thermophile" is derived from the Greek: θερμότητα, meaning heat, Greek: φίλια, love. Thermophiles can be classified in various ways. One classification sorts these organisms according to their optimal growth temperatures: Simply thermophiles: 50–64 °C Extreme thermophiles 65–79 °C Hyperthermophiles 80 °C and beyond, but not < 50 °C.
In a related classification, thermophiles are sorted as follows: Obligate thermophiles require such high temperatures for growth, whereas Facultative thermophiles can thrive at high temperatures, but at lower temperatures. Hyperthermophiles are extreme thermophiles for which the optimal temperatures are above 80 °C. Many of the hyperthermophiles Archea require elemental sulfur for growth; some are anaerobes that use the sulfur instead of oxygen as an electron acceptor during cellular respiration. Some are lithotrophs that oxidize sulphur to create sulfuric acid as an energy source, thus requiring the microorganism to be adapted to low pH; these organisms are inhabitants of hot, sulfur-rich environments associated with volcanism, such as hot springs and fumaroles. In these places in Yellowstone National Park, zonation of microorganisms according to their temperature optima occurs; these organisms are colored, due to the presence of photosynthetic pigments. Thermophiles can be discriminated from mesophiles from genomic features.
For example, the GC-content levels in the coding regions of some signatures genes were identified as correlated with the temperature range condition when the association analysis was applied to mesophilic and thermophilic organisms regardless of their phylogeny, oxygen requirement, salinity, or habitat conditions. Sulfolobus solfataricus and Sulfolobus acidocaldarius are hyperthermophilic archaea; when these organisms are exposed to the DNA damaging agents UV irradiation, bleomycin or mitomycin C, species-specific cellular aggregation is induced. In S. acidocaldarius, UV-induced cellular aggregation mediates chromosomal marker exchange with high frequency. Recombination rates exceed those of uninduced cultures by up to three orders of magnitude. Frols et al. and Ajon et al. hypothesized that cellular aggregation enhances species-specific DNA transfer between Sulfolobus cells in order to provide increased repair of damaged DNA by means of homologous recombination. Van Wolferen et al. in discussing DNA exchange in the hyperthermophiles under extreme conditions, noted that DNA exchange plays a role in repair of DNA via homologous recombination.
They suggested. It has been suggested that DNA transfer in Sulfolobus may be a primitive form of sexual interaction similar to the more well-studied bacterial transformation systems that are associated with species-specific DNA transfer between cells leading to homologous recombinational repair of DNA damage. Hyperthermophile Mesophile Psychrophile Anaerobic digestion Archaea Sulfolobus "Thermoprotei: Extreme Thermophile". NCBI Taxonomy Browser. How hot is too Hot? T-Limit Expedition