T4virus

T4virus is a genus of viruses in the order Caudovirales, in the family Myoviridae, in the subfamily Tevenvirinae. Gram-negative bacteria serve as the natural host, with transmission achieved through passive diffusion. There are currently twelve species in this genus, including the type species Enterobacteria phage T4.^[1][2][3]

Taxonomy

Group: dsDNA

^[2]

Structure

T4viruse species are nonenveloped, with a head and tail. The head is a prolate spheroid approximately 120 nm in length and 86 nm in width, with an elongated icosahedral symmetry (T=13, Q=21) composed of 152 total capsomers. The tail has 6 long terminal fibers, 6 short spikes, and a small base plate. The tail is enclosed in a sheath, which loosens and slides around the tail core upon contraction.^[1]

Genome

Genomes are linear, around 169kb in length. The genome codes for 300 proteins.^[1] Twelve of the fourteen species have been fully sequenced and are available from ICTV. They range between 159k and 235k nucleotides, with 242 to 292 proteins. The complete genomes are available from , along with the complete genome for dozens of other similar, unclassified virus strains.^[3]

Life cycle

Viral replication is cytoplasmic. The virus attaches to the host cell using its terminal fibers, and uses viral exolysin to degrade the cell wall enough to eject the viral DNA into the host cytoplasm via contraction of its tail sheath. DNA-templated transcription is the method of transcription. The virus exits the host cell by lysis, and holin/endolysin/spanin proteins. 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. Gram-negative bacteria serve as the natural host. Transmission routes are passive diffusion.^[1]

History

The ICTV's first report (1971) included the genus T-even phages, unassigned to an order, family, or subfamily. The genus was renamed in 1976 to T-even phage group, moved into the newly created family Myoviridae in 1981. In 1993, it was renamed again to T4-like phages, and was moved into the newly created order Caudovirales in 1998. The next year (1999), it was renamed to T4-like viruses. Once more, the genus was moved into the newly created subfamily Tevenvirinae in 2010-11, renamed to T4likevirus in 2012, and renamed again to T4virus in 2015. The proposals before 1993, and from 1998 are unavailable online. The other proposals are available here: 1993, 1999, 2010, 2012.^[2]

References

External links

• Viralzone: T4virus
• ICTV