Twortvirus

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Twortvirus is a genus of bacteriophages in the family Herelleviridae, subfamily Twortvirinae. Its natural hosts are bacteria, and there is one known species: Staphylococcus phage Twort (Twortvirus twort). It is named after English bacteriologist Frederick Twort.

Structure: Twortvirus particles are nonenveloped with a head and a tail. The head is about 84–94 nanometers in diameter with icosahedral symmetry (T=16). The tail is about 140–219 nanometers long, with six long terminal fibers, six short spikes, globular tip structures, and a double base plate. The tail sheath contracts to help inject the viral DNA into the host.

Life cycle: Replication happens in the host cell cytoplasm. The virus attaches to the bacterial cell via its tail fibers and injects DNA by contracting the tail sheath. Transcription uses the host’s machinery (DNA-templated). After copying its genes, the virus assembles procapsids and tails into mature virions, which are released when the cell lyses. Transmission is by passive diffusion.

Taxonomy: The genus Twortlikevirus was first accepted in the ICTV report around 2010–2011, after being proposed in 2009, and it was renamed Twortvirus in 2016. The single species in the genus is Twortvirus twort.

Genome: The genome is linear, about 130,000 to 150,000 bases long, encoding roughly 190 to 230 proteins. Complete genomes, and related genomes, are available on NCBI.