Classification of Myoviridae bacteriophages using protein sequence similarity

<jats:title>Abstract</jats:title> <jats:sec> <jats:title>Background</jats:title> <jats:p>We advocate unifying classical and genomic classification of bacteriophages by integration of proteomic data and physicochemical parameters. Our previous application of this approach to the entirely sequenced members of the <jats:italic>Podoviridae</jats:italic> fully supported the current phage classification of the International Committee on Taxonomy of Viruses (ICTV). It appears that horizontal gene transfer generally does not totally obliterate evolutionary relationships between phages.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>CoreGenes/CoreExtractor proteome comparison techniques applied to 102 <jats:italic>Myoviridae</jats:italic> suggest the establishment of three subfamilies (<jats:italic>Peduovirinae</jats:italic>, <jats:italic>Teequatrovirinae</jats:italic>, the <jats:italic>Spounavirinae</jats:italic>) and eight new independent genera (Bcep781, BcepMu, FelixO1, HAP1, Bzx1, PB1, phiCD119, and phiKZ-like viruses). The <jats:italic>Peduovirinae</jats:italic> subfamily, derived from the P2-related phages, is composed of two distinct genera: the "P2-like viruses", and the "HP1-like viruses". At present, the more complex <jats:italic>Teequatrovirinae</jats:italic> subfamily has two genera, the "T4-like" and "KVP40-like viruses". In the genus "T4-like viruses" proper, four groups sharing >70% proteins are distinguished: T4-type, 44RR-type, RB43-type, and RB49-type viruses. The <jats:italic>Spounavirinae</jats:italic> contain the "SPO1-"and "Twort-like viruses."</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusion</jats:title> <jats:p>The hierarchical clustering of these groupings provide biologically significant subdivisions, which are consistent with our previous analysis of the <jats:italic>Podoviridae</jats:italic>.</jats:p> </jats:sec>