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Virus classification
Group: Group I (dsDNA)
Family: Corticoviridae
Genus: Corticovirus

Pseudoalteromonas phage PM2

The Corticoviridae is a family of phages with a double-stranded DNA genome that infect bacteria. The name is derived from Latin cortex, corticis (meaning 'crust' or 'bark').

The family has a single genus - Corticovirus.

The type species is Alteromonas phage PM2, which is currently the only known species in this genus. However, prophages closely related to PM2 are abundant in the genomes of aquatic bacteria, suggesting that the ecological importance of corticoviruses might be underestimated.[1]

This family of viruses has been little-studied and not much is known about it.


The virons consist of a round, icosahedral, non-enveloped capsid of a diameter of 60 nm and an internal lipid membrane located between outer and inner protein shell.[2] The shells are composed of three layers whose surfaces reveals a pattern with distinctive features,[3] including bush-like spikes protruding from the twelve vertices.[4]

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.


The genome is not segmented, constitutes 13% of the virus's weight and contains a single molecule of circular, supercoiled, double-stranded DNA of 9.5-12 kilobases in length. The genome has a g + c content of 43%.[5] It encodes ~21 proteins.

Transcription is organised into three operons.

Replication of the genome is via a rolling-circle mechanism.


  1. ^ Krupovic M, Bamford DH (2007). "Putative prophages related to lytic tailless marine dsDNA phage PM2 are widespread in the genomes of aquatic bacteria". BMC Genomics 8: 236. doi:10.1186/1471-2164-8-236. PMC 1950889. PMID 17634101. 
  2. ^ Kiveld, H.M., Kalkkinen, N. and Bamford, D.H. (2002). Bacteriophage PM2 has a protein capsid surrounding a spherical lipid-protein core" J. Virol 76, 8169-8178.
  3. ^ Kiveld, H.M., Männistö, R.H., Kalkkinen, N. and Bamford, D.H. (1999). Purification and protein composition of PM2, the first lipid-containing bacterial virus to be isolated" Virology 262, 364-374.
  4. ^ Harrison, S.C., Caspar, D.L., Camerini-Otero, R.D. and Franklin, R.M. (1971). Lipid and protein arrangement in bacteriophage PM2. Nat. New Biol., 229, 197-201.
  5. ^ Männistö, R.H., Kivelä, H.M., Paulin, L., Bamford, D.H. and Bamford, J.K.H. (1999). The complete genome sequence of PM2, the first lipid-containing bacterial virus to be isolated" Virology 262, 355-363.

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