The Pseudomonas aeruginosa generalized transducing phage phiPA3 is a new member of the phiKZ-like group of 'jumbo' phages, and infects model laboratory strains and clinical isolates from cystic fibrosis patients.

Pseudomonas aeruginosa is an important pathogen in cystic fibrosis patients, and a model organism for the study of nosocomially acquired infections, biofilms and intrinsic multidrug resistance. In this study we characterize φPA3, a new generalized transducing bacteriophage for P. aeruginosa. φPA3 transduced chromosomal mutations between PAO1 strains, and infected multiple P. aeruginosa clinical isolates as well as the P. aeruginosa model laboratory strains PAK and PA14. Electron microscopy imaging was used to classify φPA3 in the order Caudovirales and the family Myoviridae. The genome of φPA3 was sequenced and found to contain 309 208 bp, the second-largest bacteriophage currently deposited in GenBank. The genome contains 378 ORFs and five tRNAs. Many ORF products in the φPA3 genome are similar to proteins encoded by P. aeruginosa phage φKZ and Pseudomonas chlororaphis phage 201φ2-1, and so φPA3 was classified genetically as a member of the φKZ-like group of phages. This is the first report of a member of this group of phages acting as a generalized transducer. Given its wide host range, high transduction efficiency and large genome size, the ‘jumbo’ phage φPA3 could be a powerful tool in functional genomic analysis of diverse P. aeruginosa strains of fundamental and clinical importance.