Archaea - Knowledge

4636:. This is suggested by the observation that archaea are resistant to a wide variety of antibiotics that are produced primarily by gram-positive bacteria, and that these antibiotics act primarily on the genes that distinguish archaea from bacteria. The proposal is that the selective pressure towards resistance generated by the gram-positive antibiotics was eventually sufficient to cause extensive changes in many of the antibiotics' target genes, and that these strains represented the common ancestors of present-day Archaea. The evolution of Archaea in response to antibiotic selection, or any other competitive selective pressure, could also explain their adaptation to extreme environments (such as high temperature or acidity) as the result of a search for unoccupied niches to escape from antibiotic-producing organisms; 630: 809: 4560: 6359: 5852:

Archaeal-specific viruses target only archaean species and currently include 12 families. Numerous unique, previously unidentified viral structures have been observed in this group, including: bottle-shaped, spindle-shaped, coil-shaped, and droplet-shaped viruses. While the reproductive cycles and genomic mechanisms of archaea-specific species may be similar to other viruses, they bear unique characteristics that were specifically developed due to the morphology of host cells they infect. Their virus release mechanisms differ from that of other phages.

237: 21254: 17962: 109: 4660: 6054: 18529: 913:"), and other similar archaea. This archaeal superphylum encompasses at least 10 different lineages and includes organisms with extremely small cell and genome sizes and limited metabolic capabilities. Therefore, DPANN may include members obligately dependent on symbiotic interactions, and may even include novel parasites. However, other phylogenetic analyses found that DPANN does not form a monophyletic group, and that the apparent grouping is caused by 6249:, with these organisms making up the majority of living cells at depths over 1 meter below the ocean bottom. It has been demonstrated that in all oceanic surface sediments (from 1000- to 10,000-m water depth), the impact of viral infection is higher on archaea than on bacteria and virus-induced lysis of archaea accounts for up to one-third of the total microbial biomass killed, resulting in the release of ~0.3 to 0.5 gigatons of carbon per year globally. 6040:

quorum sensing, some studies have uncovered LuxR proteins in archaeal species, displaying similarities with bacteria LuxR, and ultimately allowing for the detection of small molecules that are used in high density communication. Similarly to bacteria, Archaea LuxR solos have shown to bind to AHLs (lactones) and non-AHLs ligans, which is a large part in performing intraspecies, interspecies, and interkingdom communication through quorum sensing.

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organisms, leading Woese to propose the new domain of Archaea. His experiments showed that the archaea were genetically more similar to eukaryotes than prokaryotes, even though they were more similar to prokaryotes in structure. This led to the conclusion that Archaea and Eukarya shared a common ancestor more recent than Eukarya and Bacteria. The development of the nucleus occurred after the split between Bacteria and this common ancestor.

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enough to show organism-specific variations, but still small enough to be compared quickly. In 1977, Carl Woese, a microbiologist studying the genetic sequences of organisms, developed a new comparison method that involved splitting the RNA into fragments that could be sorted and compared with other fragments from other organisms. The more similar the patterns between species, the more closely they are related.

96: 5691: 9930:"Phylogenomic analyses and molecular signatures for the class Halobacteria and its two major clades: a proposal for division of the class Halobacteria into an emended order Halobacteriales and two new orders, Haloferacales ord. nov. and Natrialbales ord. nov., containing the novel families Haloferacaceae fam. nov. and Natrialbaceae fam. nov" 5177:-glycerol-3-phosphate, the phospholipid backbone found in bacteria and eukaryotes. This suggests that archaea use entirely different enzymes for synthesizing phospholipids as compared to bacteria and eukaryotes. Such enzymes developed very early in life's history, indicating an early split from the other two domains. 6039:

was originally thought to not exist in Archaea, but recent studies have shown evidence of some species being able to perform cross-talk through quorum sensing. Other studies have shown syntrophic interactions between archaea and bacteria during biofilm growth. Although research is limited in archaeal

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that is constructed across the center of the cell, are similar to their bacterial equivalents. In cren- and thaumarchaea, the cell division machinery Cdv fulfills a similar role. This machinery is related to the eukaryotic ESCRT-III machinery which, while best known for its role in cell sorting, also

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was a non-free-living organism. It may have had a permeable membrane composed of bacterial simple chain amphiphiles (fatty acids), including archaeal simple chain amphiphiles (isoprenoids). These stabilize fatty acid membranes in seawater; this property may have driven the divergence of bacterial and

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One property unique to archaea is the abundant use of ether-linked lipids in their cell membranes. Ether linkages are more chemically stable than the ester linkages found in bacteria and eukarya, which may be a contributing factor to the ability of many archaea to survive in extreme environments that

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Woese used his new rRNA comparison method to categorize and contrast different organisms. He compared a variety of species and happened upon a group of methanogens with rRNA vastly different from any known prokaryotes or eukaryotes. These methanogens were much more similar to each other than to other

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Current knowledge on genetic diversity in archaeans is fragmentary, so the total number of species cannot be estimated with any accuracy. Estimates of the number of phyla range from 18 to 23, of which only 8 have representatives that have been cultured and studied directly. Many of these hypothesized

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in the membranes of other organisms have straight chains without side branches or rings. Although isoprenoids play an important role in the biochemistry of many organisms, only the archaea use them to make phospholipids. These branched chains may help prevent archaeal membranes from leaking at high

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is key to the production of proteins in all organisms. Because this function is so central to life, organisms with mutations in their 16S rRNA are unlikely to survive, leading to great (but not absolute) stability in the structure of this polynucleotide over generations. 16S rRNA is large

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The classification of archaea, and of prokaryotes in general, is a rapidly moving and contentious field. Current classification systems aim to organize archaea into groups of organisms that share structural features and common ancestors. These classifications rely heavily on the use of the sequence

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Recently, several studies have shown that archaea exist not only in mesophilic and thermophilic environments but are also present, sometimes in high numbers, at low temperatures as well. For example, archaea are common in cold oceanic environments such as polar seas. Even more significant are the

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bacteria, largely because both have a single lipid bilayer and usually contain a thick sacculus (exoskeleton) of varying chemical composition. In some phylogenetic trees based upon different gene/protein sequences of prokaryotic homologs, the archaeal homologs are more closely related to those of

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Archaea are genetically distinct from bacteria and eukaryotes, with up to 15% of the proteins encoded by any one archaeal genome being unique to the domain, although most of these unique genes have no known function. Of the remainder of the unique proteins that have an identified function, most

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in a diverse virosphere distinct from bacterial and eukaryotic viruses. They have been organized into 15–18 DNA-based families so far, but multiple species remain un-isolated and await classification. These families can be informally divided into two groups: archaea-specific and cosmopolitan.

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that stick out from the cells' surfaces and connect them into a dense bush-like agglomeration. The function of these cannulae is not settled, but they may allow communication or nutrient exchange with neighbors. Multi-species colonies exist, such as the "string-of-pearls" community that was

782:, but by the end of the 20th century, archaea had been identified in non-extreme environments as well. Today, they are known to be a large and diverse group of organisms abundantly distributed throughout nature. This new appreciation of the importance and ubiquity of archaea came from using 4527:(the metabolic production of methane). Methanogenic archaea play a pivotal role in ecosystems with organisms that derive energy from oxidation of methane, many of which are bacteria, as they are often a major source of methane in such environments and can play a role as primary producers. 6503:, making up about one in ten of the prokaryotes in the human gut. In termites and in humans, these methanogens may in fact be mutualists, interacting with other microbes in the gut to aid digestion. Archaean communities associate with a range of other organisms, such as on the surface of 5750:

being very close to its equivalent in eukaryotes, while archaeal translation shows signs of both bacterial and eukaryotic equivalents. Although archaea have only one type of RNA polymerase, its structure and function in transcription seems to be close to that of the eukaryotic

6443:. In these anaerobic environments, protozoa break down plant cellulose to obtain energy. This process releases hydrogen as a waste product, but high levels of hydrogen reduce energy production. When methanogens convert hydrogen to methane, protozoa benefit from more energy. 16146:

Coolen MJ, Abbas B, van Bleijswijk J, Hopmans EC, Kuypers MM, Wakeham SG, et al. (April 2007). "Putative ammonia-oxidizing Crenarchaeota in suboxic waters of the Black Sea: A basin-wide ecological study using 16S ribosomal and functional genes and membrane lipids".

859:" has also been proposed, containing a small group of unusual thermophilic species sharing features of both the main phyla, but most closely related to the Thermoproteota. Other detected species of archaea are only distantly related to any of these groups, such as the 4551:

archaeal membranes, "with the later biosynthesis of phospholipids giving rise to the unique G1P and G3P headgroups of archaea and bacteria respectively. If so, the properties conferred by membrane isoprenoids place the lipid divide as early as the origin of life".

5839:. This response may be a primitive form of sexual interaction similar to the more well-studied bacterial transformation systems that are also associated with species-specific DNA transfer between cells leading to homologous recombinational repair of DNA damage. 4205:, which raises the possibility that lower temperatures are "extreme environments" for archaea, and organisms that live in cooler environments appeared only later. Since archaea and bacteria are no more related to each other than they are to eukaryotes, the term 5864:

pathways, or (rarely) a mix of the two. Most archaea-specific viral strains maintain a stable, somewhat lysogenic, relationship with their hosts – appearing as a chronic infection. This involves the gradual, and continuous, production and release of

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discovered in 2001 in a German swamp. Round whitish colonies of a novel Euryarchaeota species are spaced along thin filaments that can range up to 15 centimetres (5.9 in) long; these filaments are made of a particular bacteria species.

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hypothesis. This proposal is also supported by other work investigating protein structural relationships and studies that suggest that gram-positive bacteria may constitute the earliest branching lineages within the prokaryotes.

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Mutualism is an interaction between individuals of different species that results in positive (beneficial) effects on per capita reproduction and/or survival of the interacting populations. One well-understood example of

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between lineages. Some researchers suggest that individuals can be grouped into species-like populations given highly similar genomes and infrequent gene transfer to/from cells with less-related genomes, as in the genus

4845:. Proteins related to the cytoskeleton components of other organisms exist in archaea, and filaments form within their cells, but in contrast with other organisms, these cellular structures are poorly understood. In 11626:"Ferroplasma acidiphilum gen. nov., sp. nov., an acidophilic, autotrophic, ferrous-iron-oxidizing, cell-wall-lacking, mesophilic member of the Ferroplasmaceae fam. nov., comprising a distinct lineage of the Archaea" 6523:

showing metabolic links and evolutionary history with today's pathogens. Archaea have been inconsistently detected in clinical studies because of the lack of categorization of Archaea into more specific species.

5831:. Recombination rates exceeded 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 14713:"A putative RNA-interference-based immune system in prokaryotes: computational analysis of the predicted enzymatic machinery, functional analogies with eukaryotic RNAi, and hypothetical mechanisms of action" 5022:. In contrast with the bacterial flagellum, which is hollow and assembled by subunits moving up the central pore to the tip of the flagella, archaeal flagella are synthesized by adding subunits at the base. 5013:

across the membrane, but archaella are notably different in composition and development. The two types of flagella evolved from different ancestors. The bacterial flagellum shares a common ancestor with the

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moiety. In water, phospholipids cluster, with the heads facing the water and the tails facing away from it. The major structure in cell membranes is a double layer of these phospholipids, which is called a

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Klocke M, Nettmann E, Bergmann I, Mundt K, Souidi K, Mumme J, et al. (August 2008). "Characterization of the methanogenic Archaea within two-phase biogas reactor systems operated with plant biomass".

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groups are known from a single rRNA sequence, so the level of diversity remains obscure. This situation is also seen in the Bacteria; many uncultured microbes present similar issues with characterization.

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Parks DH, Chuvochina M, Waite DW, Rinke C, Skarshewski A, Chaumeil PA, Hugenholtz P (November 2018). "A standardized bacterial taxonomy based on genome phylogeny substantially revises the tree of life".

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Woese argued that the Bacteria, Archaea, and Eukaryotes represent separate lines of descent that diverged early on from an ancestral colony of organisms. One possibility is that this occurred before the

6156:. These groups are not comprehensive or phylum-specific, nor are they mutually exclusive, since some archaea belong to several groups. Nonetheless, they are a useful starting point for classification. 5881:, rapid mutation rates in viral genomes, and lack of universal gene sequences have led researchers to perceive the evolutionary pathway of archaeal viruses as a network. The lack of similarities among 5101:

Archaeal membranes are made of molecules that are distinctly different from those in all other life forms, showing that archaea are related only distantly to bacteria and eukaryotes. In all organisms,

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Nelson KE, Clayton RA, Gill SR, Gwinn ML, Dodson RJ, Haft DH, et al. (May 1999). "Evidence for lateral gene transfer between Archaea and bacteria from genome sequence of Thermotoga maritima".

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Gupta RS (August 1998). "What are archaebacteria: life's third domain or monoderm prokaryotes related to gram-positive bacteria? A new proposal for the classification of prokaryotic organisms".

786:(PCR) to detect prokaryotes from environmental samples (such as water or soil) by multiplying their ribosomal genes. This allows the detection and identification of organisms that have not been 3684:

found significant genetic transfer to/from less-related populations, limiting the criterion's applicability. Some researchers question whether such species designations have practical meaning.

5928:) infecting a hyperthermophilic (optimal growth at 90–95 °C) host. Notably, the latter virus has the largest currently reported ssDNA genome. Defenses against these viruses may involve 8799:

Manhesa G, Allègre CJ, Dupréa B, Hamelin B (1980). "Lead isotope study of basic-ultrabasic layered complexes: Speculations about the age of the earth and primitive mantle characteristics".

10463:"Recent events dominate interdomain lateral gene transfers between prokaryotes and eukaryotes and, with the exception of endosymbiotic gene transfers, few ancient transfer events persist" 17744: 6733: 11749:

Nickell S, Hegerl R, Baumeister W, Rachel R (January 2003). "Pyrodictium cannulae enter the periplasmic space but do not enter the cytoplasm, as revealed by cryo-electron tomography".

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and it was assumed that their metabolism reflected Earth's primitive atmosphere and the organisms' antiquity, but as new habitats were studied, more organisms were discovered. Extreme

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Yoshinari S, Itoh T, Hallam SJ, DeLong EF, Yokobori S, Yamagishi A, et al. (August 2006). "Archaeal pre-mRNA splicing: a connection to hetero-oligomeric splicing endonuclease".

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and outnumber their bacterial counterparts at salinities greater than 20–25%. Thermophiles grow best at temperatures above 45 °C (113 °F), in places such as hot springs;

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Macalady JL, Vestling MM, Baumler D, Boekelheide N, Kaspar CW, Banfield JF (October 2004). "Tetraether-linked membrane monolayers in Ferroplasma spp: a key to survival in acid".

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In some archaea, the lipid bilayer is replaced by a monolayer. In effect, the archaea fuse the tails of two phospholipid molecules into a single molecule with two polar heads (a

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Engelhardt H, Peters J (December 1998). "Structural research on surface layers: a focus on stability, surface layer homology domains, and surface layer-cell wall interactions".

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belong to the Euryarchaeota and are involved in methanogenesis. The proteins that archaea, bacteria and eukaryotes share form a common core of cell function, relating mostly to

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Mojica FJ, Díez-Villaseñor C, García-Martínez J, Soria E (February 2005). "Intervening sequences of regularly spaced prokaryotic repeats derive from foreign genetic elements".

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in this network and the global virosphere, as well as external linkages to non-viral elements, may suggest that some species of archaea specific viruses evolved from non-viral

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of the archaeal glycerol moiety is the mirror image of that found in other organisms. The glycerol moiety can occur in two forms that are mirror images of one another, called

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in the Arctic Ocean, was found to be the most closely related to eukaryotes known at that time. It has been called a transitional organism between prokaryotes and eukaryotes.

6873: 5451:, such as swamps. This form of metabolism evolved early, and it is even possible that the first free-living organism was a methanogen. A common reaction involves the use of 5144:. The difference is the type of bond that joins the lipids to the glycerol moiety; the two types are shown in yellow in the figure at the right. In ester lipids this is an 10012:"On the origins of cells: a hypothesis for the evolutionary transitions from abiotic geochemistry to chemoautotrophic prokaryotes, and from prokaryotes to nucleated cells" 5576:

is the only known phototroph archeon but it uses an alternative process to photosynthesis). Archaeal energy sources are extremely diverse, and range from the oxidation of

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and signature proteins uniquely present in either all archaea or different main groups within archaea. Another unique feature of archaea, found in no other organisms, is

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Baker BJ, Tyson GW, Webb RI, Flanagan J, Hugenholtz P, Allen EE, Banfield JF (December 2006). "Lineages of acidophilic archaea revealed by community genomic analysis".

6222:). Although these archaea can be present in extremely high numbers (up to 40% of the microbial biomass), almost none of these species have been isolated and studied in 5677:

is one-tenth of this size and the smallest archaeal genome known; it is estimated to contain only 537 protein-encoding genes. Smaller independent pieces of DNA, called

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Berg IA, Kockelkorn D, Buckel W, Fuchs G (December 2007). "A 3-hydroxypropionate/ 4-hydroxybutyrate autotrophic carbon dioxide assimilation pathway in Archaea".

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without killing the host cell. Prangishyili (2013) noted that it has been hypothesized that tailed archaeal phages originated from bacteriophages capable of infecting

11248:"This Strange Microbe May Mark One of Life's Great Leaps – A organism living in ocean muck offers clues to the origins of the complex cells of all animals and plants" 15602:

López-García P, López-López A, Moreira D, Rodríguez-Valera F (July 2001). "Diversity of free-living prokaryotes from a deep-sea site at the Antarctic Polar Front".

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Heimerl T, Flechsler J, Pickl C, Heinz V, Salecker B, Zweck J, Wanner G, Geimer S, Samson RY, Bell SD, Huber H, Wirth R, Wurch L, Podar M, Rachel R (13 June 2017).

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that make up the rest of the archaea-specific group are their own unique group in the global viral community. Krupovic et al. (2018) states that the high levels of

5796:, an extreme halophilic archaeon, forms cytoplasmic bridges between cells that appear to be used for transfer of DNA from one cell to another in either direction. 21395: 4986:, which resembles eubacterial peptidoglycan in morphology, function, and physical structure, but pseudopeptidoglycan is distinct in chemical structure; it lacks 4538:

This difference in the biochemical structure of Bacteria and Archaea has been explained by researchers through evolutionary processes. It is theorized that both

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may suggest a false similarity between them. However, structural and functional similarities between lineages often occur because of shared ancestral traits or

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are more informative because such compounds do not occur in other organisms. Some publications suggest that archaeal or eukaryotic lipid remains are present in

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Onyenwoke RU, Brill JA, Farahi K, Wiegel J (October 2004). "Sporulation genes in members of the low G+C Gram-type-positive phylogenetic branch ( Firmicutes)".

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Gogarten JP (November 1994). "Which is the most conserved group of proteins? Homology-orthology, paralogy, xenology, and the fusion of independent lineages".

10171:"Comparison of archaeal and bacterial genomes: computer analysis of protein sequences predicts novel functions and suggests a chimeric origin for the archaea" 6023:

and allow the archaea to survive in water at low salt concentrations, but these are not reproductive structures and may instead help them reach new habitats.

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Könneke M, Bernhard AE, de la Torre JR, Walker CB, Waterbury JB, Stahl DA (September 2005). "Isolation of an autotrophic ammonia-oxidizing marine archaeon".

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oxidation reactions. These reactions are particularly important in the oceans. The archaea also appear crucial for ammonia oxidation in soils. They produce

8840: 8598: 15489: 8965:"Microbially induced sedimentary structures recording an ancient ecosystem in the ca. 3.48 billion-year-old Dresser Formation, Pilbara, Western Australia" 6671:. These compounds differ in structure from bacterial antibiotics, so they may have novel modes of action. In addition, they may allow the creation of new 18170: 12210:

Ng SY, Chaban B, Jarrell KF (2006). "Archaeal flagella, bacterial flagella and type IV pili: a comparison of genes and posttranslational modifications".

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Huber H, Hohn MJ, Rachel R, Fuchs T, Wimmer VC, Stetter KO (May 2002). "A new phylum of Archaea represented by a nanosized hyperthermophilic symbiont".

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dating from 2.7 billion years ago, though such data have since been questioned. These lipids have also been detected in even older rocks from west

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Ohtomo Y, Kakegawa T, Ishida A, Nagase T, Rosingm MT (8 December 2013). "Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks".

6601:. Enzymes from these thermophilic archaea also tend to be very stable in organic solvents, allowing their use in environmentally friendly processes in 4185:, which includes Earth's oldest known sediments, formed 3.8 billion years ago. The archaeal lineage may be the most ancient that exists on Earth. 4044: 2813: 2652: 14269:

Blohs M, Moissl-Eichinger C, Mahnert A, Spang A, Dombrowski N, Krupovic M, Klingl A (January 2019). "Archaea – An Introduction". In Schmidt TM (ed.).

551:, mouth, and on the skin. Their morphological, metabolic, and geographical diversity permits them to play multiple ecological roles: carbon fixation; 10108:

Ciccarelli FD, Doerks T, von Mering C, Creevey CJ, Snel B, Bork P (March 2006). "Toward automatic reconstruction of a highly resolved tree of life".

4629: I; but the phylogeny of these genes was interpreted to reveal interdomain gene transfer, and might not reflect the organismal relationship(s). 2861: 2244: 12183:

Nguyen L, Paulsen IT, Tchieu J, Hueck CJ, Saier MH (April 2000). "Phylogenetic analyses of the constituents of Type III protein secretion systems".

5984:, the cycle has characteristics that are similar to both bacterial and eukaryotic systems. The chromosomes replicate from multiple starting points ( 20116: 18821: 18565: 6519:

Although Archaea do not have a historical reputation of being pathogens, Archaea are often found with similar genomes to more common pathogen like

5661:, but many euryarchaea have been shown to bear multiple copies of this chromosome. The largest known archaeal genome as of 2002 was 5,751,492 4064: 4004: 3904: 3864: 3815: 3263: 3095: 2789: 2738: 2197: 902: 860: 813: 415:

Archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat, square cells of

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Lipp JS, Morono Y, Inagaki F, Hinrichs KU (August 2008). "Significant contribution of Archaea to extant biomass in marine subsurface sediments".

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Moissl-Eichinger C, Pausan M, Taffner J, Berg G, Bang C, Schmitz RA (January 2018). "Archaea Are Interactive Components of Complex Microbiomes".

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Chow C, Padda KP, Puri A, Chanway CP (September 2022). "An Archaic Approach to a Modern Issue: Endophytic Archaea for Sustainable Agriculture".

6336:, methanogen archaea remove hydrogen and play an important role in the decay of organic matter by the populations of microorganisms that act as 4572: 11006: 6728: 3954: 3894: 3724: 3717: 3158: 2360: 2034: 1182: 1149: 12148:

Gophna U, Ron EZ, Graur D (July 2003). "Bacterial type III secretion systems are ancient and evolved by multiple horizontal-transfer events".

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Lykke-Andersen J, Aagaard C, Semionenkov M, Garrett RA (September 1997). "Archaeal introns: splicing, intercellular mobility and evolution".

5727:. Other characteristic archaeal features are the organization of genes of related function – such as enzymes that catalyze steps in the same 3750:

The following phyla have been proposed, but have not been validly published according to the Bacteriological Code (including those that have

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Details of the relation of Asgard members and eukaryotes are still under consideration, although, in January 2020, scientists reported that

15355:"Cell proliferation at 122 °C and isotopically heavy CH4 production by a hyperthermophilic methanogen under high-pressure cultivation" 10410:

Brown JR, Masuchi Y, Robb FT, Doolittle WF (June 1994). "Evolutionary relationships of bacterial and archaeal glutamine synthetase genes".

10229:"Protein phylogenies and signature sequences: A reappraisal of evolutionary relationships among archaebacteria, eubacteria, and eukaryotes" 3518: 5823:

could not be induced by other physical stressors, such as pH or temperature shift, suggesting that aggregation is induced specifically by

4801:(μm) to over 15 μm in diameter, and occur in various shapes, commonly as spheres, rods, spirals or plates. Other morphologies in the 21168: 10738: 7510:

Theron J, Cloete TE (2000). "Molecular techniques for determining microbial diversity and community structure in natural environments".

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In contrast with the range of applications of archaean enzymes, the use of the organisms themselves in biotechnology is less developed.

4716:. The standard hypothesis states that the ancestor of the eukaryotes diverged early from the Archaea, and that eukaryotes arose through 4695:

remains unclear. Aside from the similarities in cell structure and function that are discussed below, many genetic trees group the two.

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microbes were also included in Archaea. For a long time, archaea were seen as extremophiles that exist only in extreme habitats such as

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Some archaea are commensals, benefiting from an association without helping or harming the other organism. For example, the methanogen

5318:. These similarities to other organisms probably reflect both early origins in the history of life and their high level of efficiency. 4841:

are flat, square specimens that live in hypersaline pools. These unusual shapes are probably maintained by both their cell walls and a

12505:"Crenarchaeol: The characteristic core glycerol dibiphytanyl glycerol tetraether membrane lipid of cosmopolitan pelagic crenarchaeota" 11665:

Hall-Stoodley L, Costerton JW, Stoodley P (February 2004). "Bacterial biofilms: from the natural environment to infectious diseases".

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Synowiecki J, Grzybowska B, Zdziebło A (2006). "Sources, properties and suitability of new thermostable enzymes in food processing".

4777: 4608:, which are the object of the majority of an organism's genes, are common between Archaea and Bacteria, while most genes involved in 11586:

Hixon WG, Searcy DG (1993). "Cytoskeleton in the archaebacterium Thermoplasma acidophilum? Viscosity increase in soluble extracts".

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Gouy M, Li WH (May 1989). "Phylogenetic analysis based on rRNA sequences supports the archaebacterial rather than the eocyte tree".

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Rasmussen B, Fletcher IR, Brocks JJ, Kilburn MR (October 2008). "Reassessing the first appearance of eukaryotes and cyanobacteria".

6609:. Consequently, the counterparts of bacterial or eukaryotic enzymes from extremophile archaea are often used in structural studies. 4502:

Archaea were split off as a third domain because of the large differences in their ribosomal RNA structure. The particular molecule

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Danovaro R, Dell'Anno A, Corinaldesi C, Rastelli E, Cavicchioli R, Krupovic M, Noble RT, Nunoura T, Prangishvili D (October 2016).

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Rosenshine I, Tchelet R, Mevarech M (September 1989). "The mechanism of DNA transfer in the mating system of an archaebacterium".

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Youssefian S, Rahbar N, Van Dessel S (May 2018). "Thermal conductivity and rectification in asymmetric archaeal lipid membranes".

21382: 19822: 19376: 18285: 18260: 11150:"Genomic reconstruction of a novel, deeply branched sediment archaeal phylum with pathways for acetogenesis and sulfur reduction" 10061:"Isoprenoids enhance the stability of fatty acid membranes at the emergence of life potentially leading to an early lipid divide" 5165:. Just as a right hand does not fit easily into a left-handed glove, enantiomers of one type generally cannot be used or made by 4543: 11091:

Spang A, Saw JH, Jørgensen SL, Zaremba-Niedzwiedzka K, Martijn J, Lind AE, van Eijk R, Schleper C, Guy L, Ettema TJ (May 2015).

5683:, are also found in archaea. Plasmids may be transferred between cells by physical contact, in a process that may be similar to 4229:

The following table compares some major characteristics of the three domains, to illustrate their similarities and differences.

4165:, most prokaryotes do not have distinctive morphologies, and fossil shapes cannot be used to identify them as archaea. Instead, 21487: 15353:

Takai K, Nakamura K, Toki T, Tsunogai U, Miyazaki M, Miyazaki J, Hirayama H, Nakagawa S, Nunoura T, Horikoshi K (August 2008).

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Kostrikina NA, Zvyagintseva IS, Duda VI (1991). "Cytological peculiarities of some extremely halophilic soil archaeobacteria".

20735: 5632:. The ability of these light-driven pumps to move ions across membranes depends on light-driven changes in the structure of a 17712: 17693: 17674: 17655: 17636: 17617: 17598: 17579: 17547: 15337: 14479: 14286: 14250: 14229:

Bernstein H, Bernstein C (2017). "Sexual Communication in Archaea, the Precursor to Eukaryotic Meiosis". In Witzany G (ed.).

13612: 12874: 12132: 11835:"Natural communities of novel archaea and bacteria growing in cold sulfurous springs with a string-of-pearls-like morphology" 11400: 10732: 9986: 9770: 9533: 7347: 4581: 4197:, and that the common ancestors of the three domains arose by fixation of specific subsets of genes. It is possible that the 21387: 11930:"The ultrastructure of Ignicoccus: evidence for a novel outer membrane and for intracellular vesicle budding in an archaeon" 11893:

Thomas NA, Bardy SL, Jarrell KF (April 2001). "The archaeal flagellum: a different kind of prokaryotic motility structure".

6400:

may be a parasite of another species of archaea, since it only survives and reproduces within the cells of the Crenarchaeon

6226:. Consequently, our understanding of the role of archaea in ocean ecology is rudimentary, so their full influence on global 5560:

or another metabolic pathway called the 3-hydroxypropionate/ 4-hydroxybutyrate cycle. The Thermoproteota also use the

5204:); this fusion may make their membranes more rigid and better able to resist harsh environments. For example, the lipids in 18558: 18306: 17107:

Chelius MK, Triplett EW (April 2001). "The Diversity of Archaea and Bacteria in Association with the Roots of Zea mays L".

14090:"UV-inducible cellular aggregation of the hyperthermophilic archaeon Sulfolobus solfataricus is mediated by pili formation" 9879:"Phylogenomic analysis of proteins that are distinctive of Archaea and its main subgroups and the origin of methanogenesis" 7646:

Robertson CE, Harris JK, Spear JR, Pace NR (December 2005). "Phylogenetic diversity and ecology of environmental Archaea".

6130: 4902:

structure, but cell composition and organization set the archaea apart. Like bacteria, archaea lack interior membranes and

4576: 7554: 4582: 4578: 21101: 17858: 16007:

Liu X, Pan J, Liu Y, Li M, Gu JD (October 2018). "Diversity and distribution of Archaea in global estuarine ecosystems".

8801: 6317:

compounds release this element from rocks, making it available to other organisms, but the archaea that do this, such as

12974:

Subramaniam S, Henderson R (August 2000). "Molecular mechanism of vectorial proton translocation by bacteriorhodopsin".

11480:"An actin homolog of the archaeon Thermoplasma acidophilum that retains the ancient characteristics of eukaryotic actin" 6182:

Other archaea exist in very acidic or alkaline conditions. For example, one of the most extreme archaean acidophiles is

4575: 4565: 18494: 17855: 14194:

Fröls S, White MF, Schleper C (February 2009). "Reactions to UV damage in the model archaeon Sulfolobus solfataricus".

8734: 6700: 4579: 17820: 10585:"The neomuran origin of archaebacteria, the negibacterial root of the universal tree and bacterial megaclassification" 9222:

Brocks JJ, Logan GA, Buick R, Summons RE (August 1999). "Archean molecular fossils and the early rise of eukaryotes".

5827:. Ajon et al. showed that UV-induced cellular aggregation mediates chromosomal marker exchange with high frequency in 4577: 21158: 19695: 15578: 12546:"Recent advances in structural research on ether lipids from archaea including comparative and physiological aspects" 11786:"In vivo observation of cell division of anaerobic hyperthermophiles by using a high-intensity dark-field microscope" 9735: 5768: 4574: 4564: 4563: 708:

or subkingdoms. Woese and Fox gave the first evidence for Archaebacteria as a separate "line of descent": 1. lack of

649:

For much of the 20th century, prokaryotes were regarded as a single group of organisms and classified based on their

289: 244: 13552:"A multicopy plasmid of the extremely thermophilic archaeon Sulfolobus effects its transfer to recipients by mating" 13248:"New processes and players in the nitrogen cycle: the microbial ecology of anaerobic and archaeal ammonia oxidation" 10803:

Lake JA (January 1988). "Origin of the eukaryotic nucleus determined by rate-invariant analysis of rRNA sequences".

4580: 21444: 21163: 18603: 18321: 18301: 13365: 6198:

This resistance to extreme environments has made archaea the focus of speculation about the possible properties of

6004:

has been seen to fulfill a role in separation between divided cell, suggesting an ancestral role in cell division.

4221:

are best thought of as a grade of life, characterized by such features as an absence of membrane-bound organelles.

757: 16547:"Nanoarchaeum equitans and Ignicoccus hospitalis: new insights into a unique, intimate association of two archaea" 9021: 21413: 18598: 18551: 15637:

Karner MB, DeLong EF, Karl DM (January 2001). "Archaeal dominance in the mesopelagic zone of the Pacific Ocean".

15139:"Computational Exploration of Putative LuxR Solos in Archaea and Their Functional Implications in Quorum Sensing" 5117:"head"), and a "greasy" non-polar part that does not (the lipid tail). These dissimilar parts are connected by a 5078: 5051: 4546:. At least twice, microbes evolved lipid biosynthesis and cell wall biochemistry. It has been suggested that the 8850: 8637: 7998:

Zaremba-Niedzwiedzka K, Caceres EF, Saw JH, Bäckström D, Juzokaite L, Vancaester E, et al. (January 2017).

6823:"Rooting the domain archaea by phylogenomic analysis supports the foundation of the new kingdom Proteoarchaeota" 886:" was proposed in 2011 to be related to the origin of eukaryotes. In 2017, the newly discovered and newly named 21086: 17273:"The hunt for living gold. The search for organisms in extreme environments yields useful enzymes for industry" 15536: 6541:

archaea, particularly those resistant either to heat or to extremes of acidity and alkalinity, are a source of

5906: 4868:

Some species form aggregates or filaments of cells up to 200 μm long. These organisms can be prominent in

4612:

are common between Archaea and Eukarya. Within prokaryotes, archaeal cell structure is most similar to that of

4573: 4547: 4198: 629: 10626:"The origin of a derived superkingdom: how a gram-positive bacterium crossed the desert to become an archaeon" 6179:

Strain 116 can even reproduce at 122 °C (252 °F), the highest recorded temperature of any organism.

4569: 21074: 18682: 18672: 18655: 18405: 18270: 17193:

Gophna U, Charlebois RL, Doolittle WF (May 2004). "Have archaeal genes contributed to bacterial virulence?".

16196:, Schuster SC, Schleper C (August 2006). "Archaea predominate among ammonia-oxidizing prokaryotes in soils". 9171:

Chappe B, Albrecht P, Michaelis W (July 1982). "Polar lipids of archaebacteria in sediments and petroleums".

9031: 6705: 6077:, and may represent about 20% of microbial cells in the oceans. However, the first-discovered archaeans were 12684:

Valentine DL (April 2007). "Adaptations to energy stress dictate the ecology and evolution of the Archaea".

520:

with no other organisms. Improved molecular detection tools led to the discovery of archaea in almost every

21492: 18003: 17961: 17879: 17401:

Jenney FE, Adams MW (January 2008). "The impact of extremophiles on structural genomics (and vice versa)".

11247: 5966:

do not occur, so if a species of archaea exists in more than one form, all have the same genetic material.

5756: 5746:

Transcription in archaea more closely resembles eukaryotic than bacterial transcription, with the archaeal

5565: 5311: 4995: 497: 10760:

Eme L, Spang A, Lombard J, Stairs CW, Ettema TJG (November 2017). "Archaea and the origin of eukaryotes".

6545:

that function under these harsh conditions. These enzymes have found many uses. For example, thermostable

890:

superphylum was proposed to be more closely related to the original eukaryote and a sister group to TACK.

21246: 19815: 19369: 18346: 17761: 15791: 12593:

Hanford MJ, Peeples TL (January 2002). "Archaeal tetraether lipids: unique structures and applications".

5918: 5901: 5874: 4962:) possess a cell wall. In most archaea, the wall is assembled from surface-layer proteins, which form an 16095:

Mehta MP, Baross JA (December 2006). "Nitrogen fixation at 92 °C by a hydrothermal vent archaeon".

15561:

Davies PC (1996). "The Transfer of Viable Microorganisms Between Planets". In Bock GR, Goode JA (eds.).

14455: 11624:

Golyshina OV, Pivovarova TA, Karavaiko GI, Kondratéva TF, Moore ER, Abraham WR, et al. (May 2000).

9834:

Gupta RS, Shami A (February 2011). "Molecular signatures for the Crenarchaeota and the Thaumarchaeota".

808: 21482: 21220: 19680: 19613: 18376: 18265: 18091: 18063: 16846:

van Hoek AH, van Alen TA, Sprakel VS, Leunissen JA, Brigge T, Vogels GD, Hackstein JH (February 2000).

6685: 6495: 5667: 5230: 4520: 8703:

Göker, Markus; Oren, Aharon (11 September 2023). "Valid publication of four additional phylum names".

7999: 20590: 19959: 17780: 17158:

Simon HM, Dodsworth JA, Goodman RM (October 2000). "Crenarchaeota colonize terrestrial plant roots".

16735:

Anaerobic ciliates as a model group for studying the biodiversityand symbioses in anoxic environments

14365: 12448:"Ether- versus ester-linked phospholipid bilayers containing either linear or branched apolar chains" 9355:"Reductive evolution of architectural repertoires in proteomes and the birth of the tripartite world" 6690: 6564: 6081:. Indeed, some archaea survive high temperatures, often above 100 °C (212 °F), as found in 6062: 5807: 5740: 5015: 4698:

Complicating factors include claims that the relationship between eukaryotes and the archaeal phylum

4566: 799: 783: 642: 17826: 15202: 14142:

Ajon M, Fröls S, van Wolferen M, Stoecker K, Teichmann D, Driessen AJ, et al. (November 2011).

13956:

Watanabe Y, Yokobori S, Inaba T, Yamagishi A, Oshima T, Kawarabayasi Y, et al. (January 2002).

13630:"Sulfolobus tengchongensis spindle-shaped virus STSV1: virus-host interactions and genomic features" 13493:"The genome of Nanoarchaeum equitans: insights into early archaeal evolution and derived parasitism" 10529: 10130: 9244: 4706:" and the phylum Thermoproteota and the presence of archaea-like genes in certain bacteria, such as 4632:

It has been proposed that the archaea evolved from gram-positive bacteria in response to antibiotic

108: 21145: 21091: 19531: 18395: 18106: 16594:

Chaban B, Ng SY, Jarrell KF (February 2006). "Archaeal habitats—from the extreme to the ordinary".

15688:

Giovannoni SJ, Stingl U (September 2005). "Molecular diversity and ecology of microbial plankton".

14961:"Cdv-based cell division and cell cycle organization in the thaumarchaeon Nitrosopumilus maritimus" 9061: 8251: 8221: 8191: 5878: 5836: 5716: 5621: 5010: 4842: 4713: 4420: 3668: 845:(formerly Crenarchaeota). Other groups have been tentatively created, such as the peculiar species 438: 401: 35: 13154:

Bryant DA, Frigaard NU (November 2006). "Prokaryotic photosynthesis and phototrophy illuminated".

7960:

Guy L, Ettema TJ (December 2011). "The archaeal 'TACK' superphylum and the origin of eukaryotes".

6019:

and grow as several different cell types, including thick-walled structures that are resistant to

21180: 20044: 19654: 19647: 19633: 19538: 18972: 18687: 18532: 18446: 18441: 18336: 18250: 17998: 17872: 16889:"A psychrophilic crenarchaeon inhabits a marine sponge: Cenarchaeum symbiosum gen. nov., sp. nov" 8756:

Dalrymple GB (2001). "The age of the Earth in the twentieth century: a problem (mostly) solved".

7734:"Perspectives on archaeal diversity, thermophily and monophyly from environmental rRNA sequences" 7594:

Gevers D, Dawyndt P, Vandamme P, Willems A, Vancanneyt M, Swings J, et al. (November 2006).

5886: 5801: 5636: 5521: 5516: 4323: 1649: 1626: 787: 21449: 17538:

Shand RF, Leyva KJ (2008). "Archaeal Antimicrobials: An Undiscovered Country". In Blum P (ed.).

16545:

Jahn U, Gallenberger M, Paper W, Junglas B, Eisenreich W, Stetter KO, et al. (March 2008).

15792:"Major gradients in putatively nitrifying and non-nitrifying Archaea in the deep North Atlantic" 15412:

Ciaramella M, Napoli A, Rossi M (February 2005). "Another extreme genome: how to live at pH 0".

14603:"Archaeal virus with exceptional virion architecture and the largest single-stranded DNA genome" 14143: 11710:"Thermococcus coalescens sp. nov., a cell-fusing hyperthermophilic archaeon from Suiyo Seamount" 7337: 6761:"Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya" 5210:

are of this type, which is thought to aid this organism's survival in its highly acidic habitat.

4571: 867:

and Parvarchaeota), which were discovered in 2006 and are some of the smallest organisms known.

21477: 21270: 19808: 19362: 18487: 18431: 17988: 17978: 15197: 14959:

Pelve EA, Lindås AC, Martens-Habbena W, de la Torre JR, Stahl DA, Bernander R (November 2011).

11708:

Kuwabara T, Minaba M, Iwayama Y, Inouye I, Nakashima M, Marumo K, et al. (November 2005).

10524: 10125: 9239: 8064: 6716: 6710: 6695: 6358: 6353: 6214:

large numbers of archaea found throughout the world's oceans in non-extreme habitats among the

6153: 5280: 4919: 4570: 3661: 914: 638: 587: 17: 17495:

Norris PR, Burton NP, Foulis NA (April 2000). "Acidophiles in bioreactor mineral processing".

16946:

Eckburg PB, Bik EM, Bernstein CN, Purdom E, Dethlefsen L, Sargent M, et al. (June 2005).

13439:

Galagan JE, Nusbaum C, Roy A, Endrizzi MG, Macdonald P, FitzHugh W, et al. (April 2002).

11199:"Asgard archaea: Diversity, function, and evolutionary implications in a range of microbiomes" 10720: 6724:

Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya

21436: 20272: 19922: 19640: 19569: 18650: 18477: 18421: 18326: 18225: 18101: 18034: 14601:

Mochizuki T, Krupovic M, Pehau-Arnaudet G, Sako Y, Forterre P, Prangishvili D (August 2012).

13300: 9760: 9521: 8144:"Major New Microbial Groups Expand Diversity and Alter our Understanding of the Tree of Life" 6508: 6396: 6199: 6175: 5985: 5720: 5684: 5673: 5448: 5009:– their long stalks are driven by rotatory motors at the base. These motors are powered by a 4837: 4637: 4633: 4391: 4319: 4194: 4098: 847: 442: 417: 21426: 8814: 8080:

Williams TA, Szöllősi GJ, Spang A, Foster PG, Heaps SE, Boussau B, et al. (June 2017).

7389:

Magrum LJ, Luehrsen KR, Woese CR (May 1978). "Are extreme halophiles actually "bacteria"?".

4966:. An S-layer is a rigid array of protein molecules that cover the outside of the cell (like 4568: 21330: 21190: 19937: 19562: 18383: 18096: 17993: 17776: 17079: 17016: 16959: 16900: 16450: 16301: 16205: 16104: 16012: 15963: 15908: 15806: 15748: 15697: 15646: 15504: 15366: 14915: 14856: 14669: 14614: 14049: 13690: 13504: 13201: 13069: 12983: 12459: 12363: 11846: 11540: 11444: 11287: 11104: 11018: 10914: 10863: 10812: 10419: 10368: 10117: 9471: 9411: 9353:

Wang M, Yafremava LS, Caetano-Anollés D, Mittenthal JE, Caetano-Anollés G (November 2007).

9284: 9231: 9180: 9076: 8976: 8938: 8911: 8810: 8765: 8617: 8451: 8343: 8286: 8093: 8014: 7914: 7859: 7804: 7745: 7690: 7398: 7290: 7192: 6901: 6772: 6325:

as a waste product, and the growth of these organisms in abandoned mines can contribute to

6258: 6173:

archaea grow optimally at temperatures greater than 80 °C (176 °F). The archaeal

6016: 5945: 5764: 5629: 5525: 5220: 5180:

Archaeal lipid tails differ from those of other organisms in that they are based upon long

4991: 4626: 4567: 4416: 4210: 4182: 3702: 833:). Most of the culturable and well-investigated species of archaea are members of two main 654: 489: 422: 303: 17323:

Egorova K, Antranikian G (December 2005). "Industrial relevance of thermophilic Archaea".

16864: 16847: 14088:

Fröls S, Ajon M, Wagner M, Teichmann D, Zolghadr B, Folea M, et al. (November 2008).

11274:

Imachi H, Nobu MK, Nakahara N, Morono Y, Ogawara M, Takaki Y, et al. (January 2020).

9973:. Progress in Nucleic Acid Research and Molecular Biology. Vol. 71. pp. 223–83. 8: 21258: 20765: 19761: 19738: 19685: 19660: 19594: 19429: 18199: 17798: 15563:

Ciba Foundation Symposium 202 – Evolution of Hydrothermal Ecosystems on Earth (And Mars?)

15281:"The growing tree of Archaea: new perspectives on their diversity, evolution and ecology" 14504:"Exceptionally diverse morphotypes and genomes of crenarchaeal hyperthermophilic viruses" 13491:

Waters E, Hohn MJ, Ahel I, Graham DE, Adams MD, Barnstead M, et al. (October 2003).

13025:

Mueller-Cajar O, Badger MR (August 2007). "New roads lead to Rubisco in archaebacteria".

11478:

Hara F, Yamashiro K, Nemoto N, Ohta Y, Yokobori S, Yasunaga T, et al. (March 2007).

9026: 7183:

Zuckerkandl E, Pauling L (March 1965). "Molecules as documents of evolutionary history".

6621: 6555: 6420: 6391: 6375: 6206:, leading to the suggestion that viable microbes could be transferred between planets in 6189: 5892:

These viruses have been studied in most detail in thermophilics, particularly the orders

5882: 5658: 5561: 5472: 5250: 4983: 4945: 4885:

produce an elaborate multicell colony involving arrays of long, thin hollow tubes called

4708: 4601: 4428: 4387: 4315: 4291: 2101: 830: 741: 729: 610:

exploits enzymes from extremophile archaea that can endure high temperatures and organic

575: 385: 19800: 17083: 17020: 16963: 16904: 16498:"Identification and quantification of archaea involved in primary endodontic infections" 16454: 16305: 16209: 16108: 16016: 15967: 15912: 15810: 15752: 15701: 15650: 15508: 15370: 14919: 14860: 14673: 14618: 14405:"Advantages and Limitations of Bacteriophages for the Treatment of Bacterial Infections" 14053: 13694: 13508: 13205: 13073: 12987: 12911: 12463: 12367: 12092: 12067: 11850: 11544: 11448: 11361: 11334: 11291: 11108: 11022: 10918: 10867: 10816: 10467:

Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences

10423: 10372: 10121: 10016:

Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences

9555:

Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences

9475: 9415: 9288: 9235: 9184: 9128:

Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences

9080: 8980: 8915: 8769: 8455: 8347: 8290: 8273:

Seitz KW, Dombrowski N, Eme L, Spang A, Lombard J, Sieber JR, et al. (April 2019).

8097: 8018: 7918: 7863: 7808: 7749: 7694: 7600:

Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences

7402: 7294: 7196: 7140:

Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences

6994: 6905: 6776: 5978:

is replicated and the two daughter chromosomes separate, the cell divides. In the genus

3664:

group of interbreeding organisms — does not apply, as archaea reproduce only asexually.

21059: 20981: 20267: 19949: 18888: 18766: 18667: 18645: 18633: 18608: 18436: 18400: 18388: 18235: 18121: 18051: 18039: 18029: 17983: 17520: 17472: 17445: 17426: 17383: 17297: 17272: 17253: 17140: 17124: 17039: 17004: 16980: 16947: 16828: 16780: 16753: 16710: 16679: 16571: 16546: 16522: 16497: 16229: 16128: 16036: 15984: 15951: 15932: 15830: 15772: 15739:

DeLong EF, Karl DM (September 2005). "Genomic perspectives in microbial oceanography".

15721: 15670: 15528: 15389: 15354: 15305: 15280: 15261: 15165: 15138: 15119: 15084: 15036: 15009: 14990: 14936: 14903: 14879: 14844: 14790: 14739: 14712: 14693: 14637: 14602: 14583: 14534: 14471: 14431: 14404: 14341: 14316: 14292: 14278: 14176: 14119: 13987: 13854: 13805: 13654: 13629: 13416: 13391: 13357: 13225: 13136: 13093: 13007: 12709: 12661: 12618: 12575: 12480: 12447: 12331: 12306: 12284: 12235: 12105: 11956: 11929: 11906: 11690: 11504: 11479: 11460: 11310: 11275: 11252: 11223: 11198: 11174: 11149: 11125: 11092: 11069: 11042: 10982: 10957: 10938: 10887: 10836: 10785: 10652: 10625: 10568:

Gupta RS (2005). "Molecular Sequences and the Early History of Life". In Sapp J (ed.).

10550: 10487: 10462: 10443: 10392: 10341: 10200: 10187: 10170: 10151: 10085: 10060: 10036: 10011: 9905: 9878: 9859: 9816: 9699: 9664: 9575: 9550: 9435: 9379: 9354: 9308: 9204: 9148: 9123: 9099: 8997: 8964: 8845: 8781: 8685: 8629: 8523: 8498: 8474: 8439: 8415: 8390: 8366: 8331: 8307: 8274: 8116: 8081: 8046: 7937: 7902: 7883: 7827: 7792: 7791:

Elkins JG, Podar M, Graham DE, Makarova KS, Wolf Y, Randau L, et al. (June 2008).

7714: 7620: 7595: 7535: 7475:

DeLong EF (December 1998). "Everything in moderation: archaea as 'non-extremophiles'".

7422: 7252: 7160: 7135: 7040: 6927: 6847: 6822: 6629: 6606: 6550: 6326: 5792: 5760: 5258: 5234: 5054: 4979: 4190: 4124: 1540: 817: 319: 174: 103: 18543: 16655: 16630: 16473: 16438: 16373: 16348: 16324: 16289: 16265: 16248: 15615: 15236:

Pikuta EV, Hoover RB, Tang J (2007). "Microbial extremophiles at the limits of life".

14315:

Krupovic M, Cvirkaite-Krupovic V, Iranzo J, Prangishvili D, Koonin EV (January 2018).

13974: 13957: 13934: 13898: 13873: 13792: 13775: 13752: 13576: 13551: 13527: 13492: 13465: 13441:"The genome of M. acetivorans reveals extensive metabolic and physiological diversity" 13440: 12969: 12866: 12794: 12758: 12733: 12423: 12398: 12161: 11762: 10289: 9978: 9627: 9602: 9402:

Woese CR, Gupta R (January 1981). "Are archaebacteria merely derived 'prokaryotes'?".

9339: 8574: 8547: 7488: 7313: 7278: 6971: 6946: 21421: 21317: 21308: 21037: 20953: 20855: 20625: 20059: 19766: 19744: 19606: 19555: 19343: 19279: 19159: 19060: 18983: 18906: 18677: 18640: 18628: 18618: 18361: 18311: 18204: 18143: 18111: 18073: 18056: 17708: 17689: 17670: 17651: 17632: 17613: 17594: 17575: 17543: 17512: 17477: 17418: 17375: 17340: 17302: 17245: 17210: 17175: 17171: 17132: 17044: 16985: 16928: 16923: 16888: 16869: 16820: 16803:

Lange M, Westermann P, Ahring BK (February 2005). "Archaea in protozoa and metazoa".

16785: 16715: 16660: 16611: 16576: 16527: 16478: 16419: 16378: 16329: 16270: 16221: 16174: 16160: 16120: 16077: 16028: 15989: 15924: 15881: 15822: 15764: 15713: 15662: 15619: 15584: 15574: 15520: 15470: 15429: 15394: 15333: 15310: 15253: 15215: 15188:

DeLong EF, Pace NR (August 2001). "Environmental diversity of bacteria and archaea".

15170: 15076: 15041: 14982: 14977: 14960: 14941: 14884: 14825: 14782: 14778: 14744: 14685: 14642: 14575: 14570: 14554:"An ssDNA virus infecting archaea: a new lineage of viruses with a membrane envelope" 14553: 14526: 14475: 14436: 14385: 14346: 14317:"Viruses of archaea: Structural, functional, environmental and evolutionary genomics" 14296: 14282: 14246: 14211: 14168: 14163: 14111: 14106: 14065: 14022: 13979: 13938: 13903: 13846: 13841: 13824: 13797: 13756: 13718: 13713: 13678: 13659: 13645: 13608: 13581: 13567: 13532: 13470: 13421: 13349: 13304: 13269: 13217: 13171: 13128: 13085: 13042: 12999: 12951: 12915: 12880: 12870: 12839: 12834: 12817: 12798: 12763: 12701: 12653: 12610: 12567: 12526: 12485: 12428: 12379: 12336: 12276: 12227: 12192: 12165: 12128: 12097: 12045: 12010: 12005: 11980: 11961: 11910: 11872: 11867: 11834: 11815: 11810: 11801: 11785: 11766: 11731: 11682: 11647: 11603: 11599: 11568: 11563: 11528: 11509: 11396: 11366: 11315: 11228: 11179: 11130: 11034: 10987: 10930: 10879: 10828: 10777: 10728: 10698: 10657: 10606: 10542: 10492: 10435: 10384: 10333: 10329: 10293: 10258: 10253: 10244: 10228: 10192: 10143: 10090: 10041: 9992: 9982: 9951: 9910: 9851: 9808: 9766: 9741: 9731: 9704: 9632: 9580: 9529: 9499: 9494: 9459: 9427: 9384: 9300: 9257: 9196: 9153: 9104: 9002: 8902: 8836: 8822: 8785: 8689: 8677: 8621: 8579: 8528: 8479: 8438:

Papke RT, Zhaxybayeva O, Feil EJ, Sommerfeld K, Muise D, Doolittle WF (August 2007).

8420: 8371: 8312: 8165: 8121: 8038: 8030: 7977: 7942: 7875: 7832: 7773: 7768: 7733: 7706: 7663: 7625: 7569: 7527: 7492: 7452: 7414: 7343: 7318: 7244: 7208: 7204: 7165: 7116: 7081: 7044: 7032: 6976: 6919: 6852: 6800: 6795: 6760: 6672: 6560: 6288: 5951: 5752: 5728: 5609: 5568:. Carbon fixation is powered by inorganic energy sources. No known archaea carry out 5500: 5484: 5433: 5315: 5303: 5276: 5110: 4933: 4923: 4765: 4746: 4725: 4609: 4605: 4585: 4351: 4147: 4132: 4112: 3994: 3884: 3710: 2528: 2285: 2085: 1604: 1509: 1101: 898: 771: 713: 705: 666: 458: 430: 378: 17793: 17524: 17430: 17257: 17144: 16832: 16513: 16132: 16040: 16024: 15834: 15532: 15265: 15123: 15088: 14808:

Kelman LM, Kelman Z (September 2004). "Multiple origins of replication in archaea".

14794: 14697: 14587: 14538: 14503: 14180: 14123: 13991: 13858: 13809: 13361: 13140: 13097: 12713: 12665: 12622: 12579: 12307:"Biosynthesis of ether-type polar lipids in archaea and evolutionary considerations" 12288: 12239: 12109: 11858: 10554: 10447: 10396: 10345: 10204: 9863: 9820: 9522:"The early diversification of life and the origin of the three domains: a proposal." 9208: 8633: 8564: 7901:

Baker BJ, Comolli LR, Dick GJ, Hauser LJ, Hyatt D, Dill BD, et al. (May 2010).

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have been characterized, but hundreds more are believed to exist, especially within

762:, meaning "ancient things", as the first representatives of the domain Archaea were 661:. Microbiologists tried to classify microorganisms based on the structures of their 21472: 20335: 20214: 20106: 20049: 19989: 19984: 19912: 19897: 19700: 19498: 19493: 19469: 19287: 19217: 18592: 18331: 18255: 18189: 18044: 17504: 17467: 17457: 17410: 17387: 17367: 17332: 17292: 17284: 17237: 17202: 17167: 17116: 17087: 17034: 17024: 16975: 16967: 16918: 16908: 16859: 16812: 16775: 16765: 16705: 16695: 16650: 16646: 16642: 16603: 16566: 16558: 16517: 16509: 16468: 16458: 16409: 16368: 16360: 16319: 16309: 16260: 16233: 16213: 16193: 16164: 16156: 16112: 16067: 16020: 15979: 15971: 15936: 15916: 15871: 15861: 15814: 15776: 15756: 15725: 15705: 15674: 15654: 15611: 15566: 15512: 15460: 15421: 15384: 15374: 15300: 15292: 15245: 15207: 15160: 15150: 15111: 15068: 15031: 15021: 14994: 14972: 14931: 14923: 14874: 14864: 14817: 14774: 14734: 14724: 14677: 14632: 14622: 14565: 14518: 14467: 14426: 14416: 14377: 14336: 14332: 14328: 14274: 14238: 14203: 14158: 14101: 14057: 14014: 13969: 13930: 13893: 13885: 13836: 13787: 13748: 13708: 13698: 13649: 13641: 13571: 13563: 13522: 13512: 13460: 13452: 13411: 13403: 13341: 13296: 13259: 13229: 13209: 13163: 13120: 13077: 13034: 13011: 12991: 12943: 12907: 12862: 12829: 12790: 12753: 12749: 12745: 12693: 12645: 12602: 12557: 12516: 12475: 12467: 12418: 12410: 12399:"Structure, biosynthesis, and physicochemical properties of archaebacterial lipids" 12371: 12326: 12318: 12266: 12219: 12157: 12087: 12079: 12037: 12000: 11992: 11951: 11941: 11902: 11862: 11854: 11805: 11797: 11758: 11721: 11694: 11674: 11637: 11595: 11558: 11548: 11499: 11491: 11464: 11452: 11356: 11346: 11305: 11295: 11218: 11210: 11169: 11161: 11120: 11112: 11046: 11026: 10977: 10969: 10942: 10922: 10891: 10871: 10840: 10820: 10789: 10769: 10688: 10647: 10637: 10596: 10534: 10482: 10474: 10427: 10376: 10325: 10285: 10248: 10240: 10182: 10155: 10135: 10080: 10072: 10031: 10023: 9974: 9941: 9900: 9890: 9843: 9800: 9694: 9684: 9622: 9614: 9570: 9562: 9489: 9479: 9439: 9419: 9374: 9366: 9335: 9312: 9292: 9249: 9188: 9143: 9135: 9094: 9084: 9035: 8992: 8984: 8919: 8818: 8773: 8712: 8667: 8613: 8569: 8559: 8518: 8510: 8469: 8459: 8410: 8402: 8361: 8351: 8302: 8294: 8155: 8111: 8101: 8082:"Integrative modeling of gene and genome evolution roots the archaeal tree of life" 8050: 8022: 7969: 7932: 7922: 7867: 7822: 7812: 7763: 7753: 7718: 7698: 7655: 7615: 7607: 7539: 7519: 7484: 7426: 7406: 7308: 7298: 7236: 7200: 7155: 7147: 7108: 7071: 7024: 6966: 6958: 6931: 6909: 6842: 6834: 6790: 6780: 6617: 6374:

The well-characterized interactions between archaea and other organisms are either

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reaction), releasing energy to fuel the cell's activities. One compound acts as an

4769: 4750: 4668: 4539: 4535:, breaking down organic carbon into methane, which is also a major greenhouse gas. 4488: 4448: 4332:

Multiple, linear chromosomes, but translation and transcription similar to Archaea

4104: 3737: 3112: 3049: 1946: 1862: 887: 871: 725: 603: 544: 333: 299: 263: 212: 17288: 16364: 15850:"Uncultured archaea in deep marine subsurface sediments: have we caught them all?" 11996: 9253: 8777: 6962: 20897: 20508: 20413: 20375: 20330: 20262: 20019: 19979: 19964: 19857: 19784: 19720: 19690: 19484: 19449: 19201: 19145: 19099: 19008: 18883: 18868: 18850: 18835: 18778: 18761: 18356: 18240: 18194: 18086: 17851: 17569: 17241: 15465: 15448: 14234: 14144:"UV-inducible DNA exchange in hyperthermophilic archaea mediated by type IV pili" 12414: 9730:(4th ed.). Galveston (TX): University of Texas Medical Branch at Galveston. 6602: 6590: 6466:. Archaea associate with larger organisms, too. For example, the marine archaean 6287:) as well as processes that introduce nitrogen (such as nitrate assimilation and 6284: 6227: 5912: 5904:

that infect archaea have been recently isolated. One group is exemplified by the

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cells fuse together in culture, forming single giant cells. Archaea in the genus

4519:. Comparative analysis of archaeal genomes has also identified several molecular 4166: 4151: 3765: 3419: 3037: 2906: 2588: 2268: 1735: 1494: 1403: 1077: 548: 481: 164: 14242: 12947: 11214: 9192: 8406: 5306:

are shared among all forms of life; for example, archaea use a modified form of

4617:

gram-positive bacteria. Archaea and gram-positive bacteria also share conserved

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