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''Myoviridae'' was a family of
bacteriophage A bacteriophage (), also known informally as a phage (), is a virus that infects and replicates within bacteria. The term is derived . Bacteriophages are composed of proteins that Capsid, encapsulate a DNA or RNA genome, and may have structu ...
s 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 Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
and
archaea Archaea ( ) is a Domain (biology), domain of organisms. Traditionally, Archaea only included its Prokaryote, prokaryotic members, but this has since been found to be paraphyletic, as eukaryotes are known to have evolved from archaea. Even thou ...
serve as natural hosts. There were 625 species in this family, assigned to eight subfamilies and 217 genera.


Subdivisions

The subfamily ''Tevenvirinae'' (synonym: ''Tequatrovirinae'') is named after its
type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...
''
Enterobacteria phage T4 Escherichia virus T4 is a species of bacteriophages that infect ''Escherichia coli'' bacteria. It is a double-stranded DNA virus in the subfamily '' Tevenvirinae'' of the family '' Straboviridae''. T4 is capable of undergoing only a lytic li ...
''. 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 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 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 The Bacillota (synonym Firmicutes) are a phylum of bacteria, most of which have Gram-positive cell wall structure. They have round cells, called cocci (singular coccus), or rod-like forms (bacillus). A few Bacillota, such as '' Megasphaera'', ...
''. 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 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 the structural unit of the genome is in the order: terminase—portal—head—tail—base plate—tail fibers.


Virology

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 In molecular biology and genetics, GC-content (or guanine-cytosine content) is the percentage of nitrogenous bases in a DNA or RNA molecule that are either guanine (G) or cytosine (C). This measure indicates the proportion of G and C bases out of ...
is ~35%. The genome encodes 200-300 proteins that are transcribed in operons. 5-Hydroxymethylcytosine may be present in the genome (instead of
thymidine Thymidine (nucleoside#List of nucleosides and corresponding nucleobases, symbol dT or dThd), also known as deoxythymidine, deoxyribosylthymine, or thymine deoxyriboside, is a pyrimidine nucleoside, deoxynucleoside. Deoxythymidine is the DNA nuc ...
). 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 the tail shortens to 10–15 nm in length.


Life cycle

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 Translation is the communication of the semantics, meaning of a #Source and target languages, source-language text by means of an Dynamic and formal equivalence, equivalent #Source and target languages, target-language text. The English la ...
and begins to manufacture new viruses. Replication follows the replicative transposition model. DNA-templated transcription is the method of transcription. Translation takes place by -1 ribosomal frameshifting. The virus exits the host cell by
lysis Lysis ( ; from Greek 'loosening') is the breaking down of the membrane of a cell, often by viral, enzymic, or osmotic (that is, "lytic" ) mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a ...
, and holin/ endolysin/ spanin proteins.
Bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
and
archaea Archaea ( ) is a Domain (biology), domain of organisms. Traditionally, Archaea only included its Prokaryote, prokaryotic members, but this has since been found to be paraphyletic, as eukaryotes are known to have evolved from archaea. Even thou ...
serve as the natural host. Transmission route is passive
diffusion Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...
. Although Myoviruses are in general
lytic The lytic cycle ( ) is one of the two cycles of viral reproduction (referring to bacterial viruses or bacteriophages), the other being the lysogenic cycle. The lytic cycle results in the destruction of the infected cell and its membrane. Bact ...
, lacking the genes required to become lysogenic, a number of
temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...
species are known.


Applications

Because most ''Myoviridae'' are lytic, rather than temperate, phages, some researchers have investigated their use as a therapy for bacterial diseases in humans and other animals.


Taxonomy

The following eight subfamilies are recognized: * '' Emmerichvirinae'' * '' Eucampyvirinae'' * '' Gorgonvirinae'' * '' Ounavirinae'' * '' Peduovirinae'' * '' Tevenvirinae'' * '' Twarogvirinae'' * '' Vequintavirinae'' Additionally, the following genera are unassigned to a subfamily: * '' Abouovirus'' * '' Acionnavirus'' * '' Agricanvirus'' * '' Ahtivirus'' * '' Alcyoneusvirus'' * '' Alexandravirus'' * '' Anamdongvirus'' * '' Anaposvirus'' * '' Aokuangvirus'' * '' Asteriusvirus'' * '' Atlauavirus'' * '' Aurunvirus'' * '' Ayohtrevirus'' * '' Baikalvirus'' * '' Bakolyvirus'' * '' Barbavirus'' * '' Bcepfunavirus'' * '' Bcepmuvirus'' * '' Becedseptimavirus'' * '' Bellamyvirus'' * '' Bendigovirus'' * '' Biquartavirus'' * '' Bixzunavirus'' * '' Borockvirus'' * '' Brigitvirus'' * '' Brizovirus'' * '' Brunovirus'' * '' Busanvirus'' * '' Carpasinavirus'' * '' Chakrabartyvirus'' * '' Charybdisvirus'' * '' Chiangmaivirus'' * '' Colneyvirus'' * '' Cymopoleiavirus'' * '' Derbicusvirus'' * '' Dibbivirus'' * '' Donellivirus'' * '' Elmenteitavirus'' * '' Elvirus'' * '' Emdodecavirus'' * '' Eneladusvirus'' * '' Eponavirus'' * '' Erskinevirus'' * '' Eurybiavirus'' * '' Ficleduovirus'' * '' Flaumdravirus'' * '' Fukuivirus'' * '' Gofduovirus'' * '' Goslarvirus'' * '' Haloferacalesvirus'' * '' Hapunavirus'' * '' Heilongjiangvirus'' * '' Iapetusvirus'' * '' Iodovirus'' * '' Ionavirus'' * '' Jedunavirus'' * '' Jilinvirus'' * '' Jimmervirus'' * '' Kanagawavirus'' * '' Kanaloavirus'' * '' Klausavirus'' * '' Kleczkowskavirus'' * '' Kungbxnavirus'' * '' Kylevirus'' * '' Lagaffevirus'' * '' Leucotheavirus'' * '' Libanvirus'' * '' Lietduovirus'' * '' Llyrvirus'' * '' Loughboroughvirus'' * '' Lubbockvirus'' * '' Machinavirus'' * '' Marfavirus'' * '' Marthavirus'' * '' Mazuvirus'' * '' Menderavirus'' * '' Metrivirus'' * '' Mieseafarmvirus'' * '' Mimasvirus'' * '' Moabitevirus'' * '' Moturavirus'' * '' Muldoonvirus'' * '' Mushuvirus'' * '' Muvirus'' * '' Myoalterovirus'' * '' Myohalovirus'' * '' Myosmarvirus'' * '' Naesvirus'' * '' Namakavirus'' * '' Nankokuvirus'' * '' Neptunevirus'' * '' Nereusvirus'' * '' Nerrivikvirus'' * '' Nodensvirus'' * '' Noxifervirus'' * '' Nylescharonvirus'' * '' Obolenskvirus'' * '' Otagovirus'' * '' Pakpunavirus'' * '' Palaemonvirus'' * '' Pbunavirus'' * '' Peatvirus'' * '' Pemunavirus'' * '' Petsuvirus'' * '' Phabquatrovirus'' * '' Phapecoctavirus'' * '' Phikzvirus'' * '' Pippivirus'' * '' Plaisancevirus'' * '' Plateaulakevirus'' * '' Polybotosvirus'' * '' Pontusvirus'' * '' Popoffvirus'' * '' Punavirus'' * '' Qingdaovirus'' * '' Rahariannevirus'' * '' Radnorvirus'' * '' Ripduovirus'' * '' Risingsunvirus'' * '' Ronodorvirus'' * '' Rosemountvirus'' * '' Saclayvirus'' * '' Saintgironsvirus'' * '' Salacisavirus'' * '' Salmondvirus'' * '' Sarumanvirus'' * '' Sasquatchvirus'' * '' Schmittlotzvirus'' * '' Seoulvirus'' * '' Shandongvirus'' * '' Sherbrookevirus'' * '' Shirahamavirus'' * '' Shalavirus'' * '' Svunavirus'' * '' Tabernariusvirus'' * '' Takahashivirus'' * '' Tamkungvirus'' * '' Taranisvirus'' * '' Tefnutvirus'' * '' Tegunavirus'' * '' Thaumasvirus'' * '' Thetisvirus'' * '' Thornevirus'' * '' Tijeunavirus'' * '' Toutatisvirus'' * '' Tulanevirus'' * '' Vellamovirus'' * '' Vhmlvirus'' * '' Vibakivirus'' * '' Wellingtonvirus'' * '' Wifcevirus'' * '' Winklervirus'' * '' Yokohamavirus'' * '' Yoloswagvirus'' * '' Yongloolinvirus''


References


External links


Viralzone: Myoviridae

ICTV

Complete Genomes of Myoviridae
Virus families {{Italictitle