''Corticovirus'' is a genus of

viruses A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's ...

in the family '' Corticoviridae''. Corticoviruses are bacteriophages; that is, their natural

hosts A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places *Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman *Michel Host ( ...

are

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...

. The genus contains two species. The name is derived from Latin ''cortex'', ''corticis'' (meaning 'crust' or 'bark'). However, prophages closely related to PM2 are abundant in the genomes of aquatic bacteria, suggesting that the ecological importance of corticoviruses might be underestimated. Bacteriophage PM2 was first described in 1968 after isolation from

seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appr ...

sampled from the coast of

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

Taxonomy

The genus contains the following species: * '' Pseudoalteromonas virus Cr39582'' * '' Pseudoalteromonas virus PM2'' Other unassigned phages: * '' Pseudoalteromonas virus GXT1010'' * '' Marinomonas virus YY'' * '' Vibrio virus fNo16''

Virology

The virons consist of a round,

icosahedral In geometry, an icosahedron ( or ) is a polyhedron with 20 faces. The name comes and . The plural can be either "icosahedra" () or "icosahedrons". There are infinitely many non- similar shapes of icosahedra, some of them being more symmetrica ...

, non-enveloped

capsid A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or ma ...

of a diameter of 60 nm and an internal

lipid Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids includ ...

membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. ...

located between outer and inner

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

shell. The shells are composed of three layers whose surfaces reveals a pattern with distinctive features, including bush-like spikes protruding from the twelve vertices. The icosahedral capsid (T = 21) is 56 nanometers (nm) in diameter and is composed of 1200 P1 (spike) and 60 P2 (capsid) proteins. The pentameric receptor-binding spikes protrude from the 12 fivefold axes. The capsid encloses an internal lipid core containing the structural proteins P3 to P10.

Genome

The genome is not segmented, constitutes 13% of the virus's weight and contains a single molecule of circular, supercoiled, double-stranded DNA of 10 kilo bases in length. The genome has a g + c content of 43%. It encodes ~21 proteins. Transcription is organised into three operons. Replication of the genome is via a rolling-circle mechanism, initiated by the virus encoded endonuclease P12.

Life cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by adsorption to the host cell surface followed by fusion of the viral membrane with the outer membrane of the host cell and subsequent genome delivery into the cell interior. DNA-templated transcription is the method of transcription. Bacteria of the genera '' Pseudoalteromonas'', '' Marinomonas'' and ''

Vibrio ''Vibrio'' is a genus of Gram-negative bacteria, possessing a curved-rod (comma) shape, several species of which can cause foodborne infection, usually associated with eating undercooked seafood. Being highly salt tolerant and unable to survive ...

'' serve as the natural host. Corticovirus PM2 is a lytic virus and at the end of the infection cycle disrupts the host cell using a unique lysis system consisting of phage-encoded proteins P17 and P18 as well as an unidentified host autolysin. However, identification of PM2-like proviruses in bacterial genomes indicates that other members of this family might be temperate viruses. Transmission routes are passive diffusion.

References

External links

ICTV Online(10th) Report: Corticoviridae

{{Taxonbar, from=Q1135608 Bacteriophages Virus genera