Characterization of Pseudomonas chlororaphis myovirus 201ϕ2-1 via genomic sequencing, mass spectrometry, and electron microscopy

Pseudomonas chlororaphis phage 201ϕ2-1 is a relative of Pseudomonas aeruginosa myovirus ϕKZ. Phage 201ϕ2-1 was examined by complete genomic sequencing (316,674 bp), by a comprehensive mass spectrometry survey of its virion proteins and by electron microscopy. Seventy-six proteins, of which at least 69 have homologues in ϕKZ, were identified by mass spectrometry. Eight proteins, in addition to the major head, tail sheath and tail tube proteins, are abundant in the virion. Electron microscopy of 201ϕ2-1 revealed a multitude of long, fine fibers apparently decorating the tail sheath protein. Among the less abundant virion proteins are three homologues to RNA polymerase β or β′ subunits. Comparison between the genomes of 201ϕ2-1 and ϕKZ revealed substantial conservation of the genome plan, and a large region with an especially high rate of gene replacement. The ϕKZ-like phages exhibited a two-fold higher rate of divergence than for T4-like phages or host genomes.