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25-441: Myoviridae was a family of bacteriophages in the order Caudovirales . The family Myoviridae and order Caudovirales have now been abolished, with the term myovirus now used to refer to the morphology of viruses in this former family. Bacteria and archaea serve as natural hosts. There were 625 species in this family, assigned to eight subfamilies and 217 genera. The subfamily Tevenvirinae (synonym: Tequatrovirinae )
50-400: A head length of 137 nm and those in the genus Schizotequatrovirus being 111 nm in length. Within the genera on the basis of protein homology the species have been divided into a number of groups. The subfamily Peduovirinae have virions with heads of 60 nm in diameter and tails of 135 × 18 nm. These phages are easily identified because contracted sheaths tend to slide off
75-571: A long time, archaea were seen as extremophiles that exist only in extreme habitats such as hot springs and salt lakes , 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 polymerase chain reaction (PCR) to detect prokaryotes from environmental samples (such as water or soil) by multiplying their ribosomal genes. This allows
100-578: 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 Archaeal Richmond Mine acidophilic nanoorganisms (ARMAN, comprising Micrarchaeota and Parvarchaeota), which were discovered in 2006 and are some of the smallest organisms known. A superphylum – TACK – which includes
125-665: A therapy for bacterial diseases in humans and other animals. The following eight subfamilies are recognized: Additionally, the following genera are unassigned to a subfamily: Bacteriophage Too Many Requests If you report this error to the Wikimedia System Administrators, please include the details below. Request from 172.68.168.132 via cp1112 cp1112, Varnish XID 392659216 Upstream caches: cp1112 int Error: 429, Too Many Requests at Fri, 29 Nov 2024 05:37:27 GMT Archaea Archaea ( / ɑːr ˈ k iː ə / ar- KEE -ə )
150-682: Is a domain of organisms . Traditionally, Archaea only included its prokaryotic members, but this sense has been found to be paraphyletic , as eukaryotes are now known to have evolved from archaea. Even though the domain Archaea includes eukaryotes, the term "archaea" ( sg. : archaeon / ɑːr ˈ k iː ɒ n / ar- KEE -on , from the Greek "αρχαίον", which means ancient) in English still generally refers specifically to prokaryotic members of Archaea. Archaea were initially classified as bacteria , receiving
175-675: Is derived from SPO plus una (Latin for one). The haloviruses HF1 and HF2 belong to the same genus but since they infect archaea rather than bacteria are likely to be placed in a separate genus once their classification has been settled. A dwarf group has been proposed on morphological and genomic grounds. This group includes the phages Aeromonas salmonicida phage 56, Vibrio cholerae phages 138 and CP-T1, Bdellovibrio phage φ1422 and Pectobacterium carotovorum phage ZF40. Their shared characteristics include an identical virion morphology, characterized by usually short contractile tails and all have genome sizes of approximately 45 kilobases. The gene order in
200-448: Is named after its type species Enterobacteria phage T4 . Members of this subfamily are morphologically indistinguishable and have moderately elongated heads of about 110 nanometers (nm) in length, 114 nm long tails with a collar, base plates with short spikes and six long kinked tail fibers. The genera within this subfamily are divided on the basis of head morphology with the genus Tequatrovirus (Provisional name: T4virus ) having
225-525: Is the method of transcription. Translation takes place by -1 ribosomal frameshifting . The virus exits the host cell by lysis , and holin / endolysin / spanin proteins. Bacteria and archaea serve as the natural host. Transmission route is passive diffusion . Although Myoviruses are in general lytic , lacking the genes required to become lysogenic , a number of temperate species are known. Because most Myoviridae are lytic, rather than temperate, phages, some researchers have investigated their use as
250-405: Is unknown if they are able to produce endospores . 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 Haloquadratum walsbyi . Despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for
275-894: The enzymes involved in transcription and translation . Other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes , including archaeols . Archaea use more diverse energy sources than eukaryotes, ranging from organic compounds such as sugars, to ammonia , metal ions or even hydrogen gas . The salt-tolerant Haloarchaea use sunlight as an energy source, and other species of archaea fix carbon (autotrophy), but unlike plants and cyanobacteria , no known species of archaea does both. Archaea reproduce asexually by binary fission , fragmentation , or budding ; unlike bacteria, no known species of Archaea form endospores . The first observed archaea were extremophiles , living in extreme environments such as hot springs and salt lakes with no other organisms. Improved molecular detection tools led to
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#1732858646984300-525: The gastrointestinal tract in humans and ruminants , where their vast numbers facilitate digestion . Methanogens are also used in biogas production and sewage treatment , and biotechnology exploits enzymes from extremophile archaea that can endure high temperatures and organic solvents . For much of the 20th century, prokaryotes were regarded as a single group of organisms and classified based on their biochemistry , morphology and metabolism . Microbiologists tried to classify microorganisms based on
325-589: The methanogens were known). They called these groups the Urkingdoms of Archaebacteria and Eubacteria, though other researchers treated them as kingdoms or subkingdoms. Woese and Fox gave the first evidence for Archaebacteria as a separate "line of descent": 1. lack of peptidoglycan in their cell walls, 2. two unusual coenzymes, 3. results of 16S ribosomal RNA gene sequencing. To emphasize this difference, Woese, Otto Kandler and Mark Wheelis later proposed reclassifying organisms into three natural domains known as
350-768: The three-domain system : the Eukarya , the Bacteria and the Archaea, in what is now known as the Woesian Revolution . The word archaea comes from the Ancient Greek ἀρχαῖα , meaning "ancient things", as the first representatives of the domain Archaea were methanogens 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 halophilic and hyperthermophilic microbes were also included in Archaea. For
375-1003: The Thaumarchaeota (now Nitrososphaerota ), " Aigarchaeota ", Crenarchaeota (now Thermoproteota ), and " Korarchaeota " was proposed in 2011 to be related to the origin of eukaryotes. In 2017, the newly discovered and newly named Asgard superphylum was proposed to be more closely related to the original eukaryote and a sister group to TACK. In 2013, the superphylum DPANN was proposed to group " Nanoarchaeota ", " Nanohaloarchaeota ", Archaeal Richmond Mine acidophilic nanoorganisms (ARMAN, comprising " Micrarchaeota " and " Parvarchaeota "), 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
400-455: The culturable and well-investigated species of archaea are members of two main phyla , the " Euryarchaeota " and the Thermoproteota (formerly Crenarchaeota). Other groups have been tentatively created, such as the peculiar species Nanoarchaeum equitans — discovered in 2003 and assigned its own phylum, the " Nanoarchaeota ". A new phylum " Korarchaeota " has also been proposed, containing
425-502: The detection and identification of organisms that have not been cultured in the laboratory. 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 of ribosomal RNA genes to reveal relationships among organisms ( molecular phylogenetics ). Most of
450-412: The discovery of archaea in almost every habitat , including soil, oceans, and marshlands . Archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. Archaea are a major part of Earth's life . They are part of the microbiota of all organisms. In the human microbiome , they are important in the gut , mouth, and on
475-431: The genome (instead of thymidine ). The tubular tail has helical symmetry and is 16-20 nm in diameter. It consists of a central tube, a contractile sheath, a collar, a base plate, six tail pins and six long fibers. It is similar to Tectiviridae , but differs in the fact that a myovirus' tail is permanent. Contractions of the tail require ATP . On contraction of the sheath, sheath subunits slide over each other and
500-519: The name archaebacteria ( / ˌ ɑːr k i b æ k ˈ t ɪər i ə / , in the Archaebacteria kingdom ), but this term has fallen out of use. Archaeal cells have unique properties separating them from Bacteria and Eukaryota . Archaea are further divided into multiple recognized phyla . Classification is difficult because most have not been isolated in a laboratory and have been detected only by their gene sequences in environmental samples. It
525-454: The skin. Their morphological, metabolic, and geographical diversity permits them to play multiple ecological roles: carbon fixation; nitrogen cycling ; organic compound turnover; and maintaining microbial symbiotic and syntrophic communities, for example. No clear examples of archaeal pathogens or parasites are known. Instead they are often mutualists or commensals , such as the methanogens (methane-producing strains) that inhabit
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#1732858646984550-492: The structural unit of the genome is in the order: terminase—portal—head—tail—base plate—tail fibers. Viruses in the former family Myoviridae are non-enveloped, with head-tail (with a neck) geometries. Genomes are linear, double-stranded DNA, around 33-244kb in length. The genome codes for 40 to 415 proteins. It has terminally redundant sequences. The GC-content is ~35%. The genome encodes 200-300 proteins that are transcribed in operons. 5-Hydroxymethylcytosine may be present in
575-488: The structures of their cell walls , their shapes, and the substances they consume. In 1965, Emile Zuckerkandl and Linus Pauling instead proposed using the sequences of the genes in different prokaryotes to work out how they are related to each other. This phylogenetic approach is the main method used today. Archaea were first classified separately from bacteria in 1977 by Carl Woese and George E. Fox , based on their ribosomal RNA (rRNA) genes. (At that time only
600-636: The tail core. The P" phage is the type species. The subfamily Spounavirinae are all virulent, broad-host range phages that infect members of the Bacillota . They possess isometric heads of 87-94 nm in diameter and conspicuous capsomers , striated 140-219 nm long tails and a double base plate. At the tail tip are globular structures now known to be the base plate spikes and short kinked tail fibers with six-fold symmetry. Members of this group usually possess large (127–142 kb) nonpermuted genomes with 3.1–20 kb terminal redundancies. The name for this subfamily
625-442: The tail shortens to 10–15 nm in length. On attaching to a host cell, the virus uses its contractile sheath like a syringe, piercing the cell wall with its central tube and injecting the genetic material into the host. The injected DNA takes over the host cell's mechanisms for transcription and translation and begins to manufacture new viruses. Replication follows the replicative transposition model. DNA-templated transcription
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