Phikzvirus

Phikzvirus (synonym: PhiKZ-like viruses, Phikzlikevirus before 2015) is a genus of viruses in the order Caudovirales, in the family Myoviridae. Bacteria serve as natural hosts. There are currently three species in this genus, including the type species Pseudomonas virus phiKZ (aka Pseudomonas phage phiKZ).[1][2][3]

Phikzvirus
Virus classification
(unranked): Virus
Realm: Duplodnaviria
Kingdom: Heunggongvirae
Phylum: Uroviricota
Class: Caudoviricetes
Order: Caudovirales
Family: Myoviridae
Genus: Phikzvirus
Type species
Pseudomonas virus phiKZ

Phages in this genus are considered large or "jumbo" phages. Three phages in this genus (φKZ, φPA3, and 201φ2-1) are known to assemble a "phage nucleus" structure similar in function to the eukaryotic cell nucleus that encloses DNA as well as replication and transcription machinery. These structures are built from a tubulin-like PhuZ protein and a gp105 shell protein. It provides immunity to host defenses like restriction enzymes and CRISPR-Cas systems.[4]

Taxonomy

Group: dsDNA

[2]

Structure

Phikzviruses are nonenveloped, with a head and tail. The head has icosahedral symmetry (T=27), with a relatively large diameter of about 140  nm. The tail is around 160 nm long, 35 nm wide.[1]

GenusStructureSymmetryCapsidGenomic arrangementGenomic segmentation
PhikzvirusHead-TailT=27Non-envelopedCircularMonopartite

Genome

Genomes are circular, around 280kb in length.[1] Two of the three species have been fully sequenced and are available from ICTV; the exclusion is Pseudomonas phage Lin68. They range between 211k and 280k nucleotides, with 201 to 306 proteins. The complete genomes, along with one other similar but unclassified genome, are available here.[3]

Life cycle

Viral replication is cytoplasmic. The virus attaches to the host cell using its terminal fibers, and ejects the viral DNA into the host cytoplasm via contraction of its tail sheath. DNA-templated transcription is the method of transcription. Once the viral genes have been replicated, the procapsid is assembled and packed. The tail is then assembled and the mature virions are released via lysis. Bacteria serve as the natural host. Transmission routes are passive diffusion.[1]

GenusHost detailsTissue tropismEntry detailsRelease detailsReplication siteAssembly siteTransmission
PhikzvirusBacteriaNoneInjectionLysisCytoplasmCytoplasmPassive diffusion

History

According to the ICTV's 2009 report, the genus PhiKZ-like viruses was first accepted as a new genus, at the same time as all three of its contained species. This proposal is available here. In 2012, the name was changed to Phikzlikevirus. This proposal is available here.[5] The genus was later renamed Phikzvirus.

References
  1. "Viral Zone". ExPASy. Retrieved 1 July 2015.
  2. ICTV. "Virus Taxonomy: 2014 Release". Retrieved 1 July 2015.
  3. NCBI. "Phikzlikevirus Complete Genomes". Retrieved 17 February 2015.
  4. Chaikeeratisak, V; Nguyen, K; Egan, ME; Erb, ML; Vavilina, A; Pogliano, J (15 August 2017). "The Phage Nucleus and Tubulin Spindle Are Conserved among Large Pseudomonas Phages". Cell Reports. 20 (7): 1563–1571. doi:10.1016/j.celrep.2017.07.064. PMC 6028189. PMID 28813669.
  5. ICTV. "Virus Taxonomy: 2013 Release". Retrieved 17 February 2015.

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