T7 phages
| Enterobacteria phage T7 | |
|---|---|
| Virus classification | |
| Group: | Group I (dsDNA) |
| Order: | Caudovirales |
| Family: | Podoviridae |
| Genus: | T7-like viruses |
| Species: | T7 phage |
Bacteriophage T7 (or the T7 phage) is a bacteriophage, a virus that infects susceptible bacterial cells, that is composed of DNA and infects most strains of Escherichia coli. Bacteriophage T7 has a lytic life cycle and several properties that make it an ideal phage for experimentation.
Bacteriophage T7 was identified in 1945 as a member of the seven Type (“T”) phages that grow lytically on Escherichia coli B, although it is probably identical to phage δ, used earlier by Delbrück. A close relative of T7 was likely studied by d’Herelle in the 1920s.
T7 grows on rough strains of E. coli (i.e. those without full-length O-antigen polysaccharide on their surface) and some other enteric bacteria, but close relatives also infect smooth and even capsulated strains. It infects E. coli O157:H7, a strain of E. coli that can cause foodborne illness).
The virus has complex structural symmetry, with a capsid of the phage that is icosahedral with an inner diameter of 55 nm and a tail 19 nm in diameter and 28.5 nm long attached to the capsid.
The genome of phage T7 was among the first completely sequenced genomes and was published in 1983. The head of the phage particle contains the roughly 40 kbp dsDNA genome which encodes 55 proteins.
![Schematic view of the phage T7 genome. Boxes are genes, numbers are gene numbers. Colors indicate functional groups as shown. White boxes are genes of unknown function or without annotation. Modified after [7]](https://en.wikipedia.org/wiki/File:T7_phage_genome.png)
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