Phenogenetic characterization of a group of giant φKZ-like bacteriophages of Pseudomonas aeruginosa

A comparative study was made of a group of Pseudomonas aeruginosa virulent giant DNA bacteriophages similar to phage phiKZ in several genetic and phenotypic properties (particle size, particle morphology, genome size, appearance of negative colonies, high productivity, broad spectrum of lytic activity, ability to overcome the suppressing effect of plasmids, absence of several DNA restriction sites, capability of general transduction, pseudolysogeny). We have recently sequenced the phage phiKZ genome (288 334 bp) [J. Mol. Biol., 2002, vol. 317, pp. 1-19]. By DNA homology, the phages were assigned to three species (represented by phages phiKZ, Lin68, and EL, respectively) and two new genera (phiKZ and EL). Restriction enzyme analysis revealed the mosaic genome structure in four phages of the phiKZ species (phiKZ, Lin21, NN, and PTB80) and two phages of the EL species (EL and RU). Comparisons with respect to phage particle size, number of structural proteins, and the N-terminal sequences of the major capsid protein confirmed the phylogenetic relatedness of the phages belonging to the phiKZ genus. The origin and evolution of the phiKZ-like phages are discussed. Analysis of protein sequences encoded by the phage phiKZ genome made it possible to assume wide migration of the phiKZ-like phages (wandering phages) among various prokaryotes and possibly eukaryotes. Since the phage phiKZ genome codes for potentially toxic proteins, caution must be exercised in the employment of large bacteriophages in phage therapy.