Members of this subfamily generally infect Staphylococcus and Lactobacillus strains, and have genomes of 135–150 kbp.
Derivation of names
Twortvirinae: named in honour of Frederick William Twort (1877–1950), the English bacteriologist who discovered prokaryotic viruses in 1915.
Genus demarcation criteria
The Twortvirinae genera are well-supported monophyletic clades in genome-based phylogenies and in (concatenated) marker gene phylogenies. Members of the genera share at least 60% nucleotide identity across the genome length. The genome organisation is conserved. Members of the same genus generally infect members of the same bacterial genus.
Note that the genus Harbinvirus has been misplaced in the subfamily Twortvirinae; the Taxonomic Proposal 2020.072B.N.V1.Herelleviridae has been submitted to the ICTV to change it to an orphan genus in the family.