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Siphoviridae

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Siphoviridae
TME picture of an Escherichia virus HK97 virion, Siphoviridae
Virus classification Edit this classification
(unranked): Virus
Realm: Duplodnaviria
Kingdom: Heunggongvirae
Phylum: Uroviricota
Class: Caudoviricetes
Order: Caudovirales
Family: Siphoviridae
Genera

see text

Synonyms[1]
  • Styloviridae

Siphoviridae is a family of double-stranded DNA viruses in the order Caudovirales. Bacteria and archaea serve as natural hosts. There are 1,166 species in this family, assigned to 366 genera and 22 subfamilies.[2][3] The characteristic structural features of this family are a nonenveloped head and noncontractile tail.

Structure

Typical structure of a siphovirus

Viruses in Siphoviridae are non-enveloped, with icosahedral and head-tail geometries[2] (morphotype B1) or a prolate capsid (morphotype B2), and T=7 symmetry. The diameter is around 60 nm.[2] Members of this family are also characterized by their filamentous, cross-banded, noncontractile tails, usually with short terminal and subterminal fibers. Genomes are double stranded and linear, around 50 kb in length,[2] containing about 70 genes. The guanine/cytosine content is usually around 52%.[citation needed]

Life cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by adsorption into the host cell. Replication follows the replicative transposition model. DNA-templated transcription is the method of transcription. Translation takes place by -1 ribosomal frameshifting, and +1 ribosomal frameshifting. The virus exits the host cell by lysis, and holin/endolysin/spanin proteins.[2] Bacteria and archaea serve as the natural host. Transmission routes are passive diffusion.[2]

Taxonomy

Electron micrographs of siphovirus from Cutibacterium acnes (formerly Propionibacterium acnes). Phages were negatively stained and subjected to transmission electron microscopy. The phages have a head of approximately 55 nm in diameter, loaded with genetic material. Their tails have a size of 150 × 10 nm and are flexible and non-contractile. In the lower micrograph, PAD25 is adhering to bacterial cell debris, and two phages have lost their heads. All phages were classified as Siphoviruses based on their morphology.[4]

The following subfamilies are recognized:[3]

The following genera are unassigned to a subfamily:[3]

Please note that genus Inceonvirus is likely misspelled Incheonvrus.

References

  1. ^ Safferman, R.S.; Cannon, R.E.; Desjardins, P.R.; Gromov, B.V.; Haselkorn, R.; Sherman, L.A.; Shilo, M. (1983). "Classification and Nomenclature of Viruses of Cyanobacteria". Intervirology. 19 (2): 61–66. doi:10.1159/000149339. PMID 6408019.
  2. ^ a b c d e f "Viral Zone". ExPASy. Retrieved 1 July 2015.
  3. ^ a b c "Virus Taxonomy: 2020 Release". International Committee on Taxonomy of Viruses (ICTV). March 2021. Retrieved 12 May 2021.
  4. ^ Lood R, Mörgelin M, Holmberg A, Rasmussen M, Collin M (2008). "Inducible Siphoviruses in superficial and deep tissue isolates of Propionibacterium acnes". BMC Microbiol. 8: 139. doi:10.1186/1471-2180-8-139. PMC 2533672. PMID 18702830.{{cite journal}}: CS1 maint: unflagged free DOI (link)
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