Genomic analysis of Pseudomonas aeruginosa phages LKD16 and LKA1:: Establishment of the φKMV subgroup within the T7 supergroup

Lytic Pseudomonas aeruginosa phages LKD16 and LKA1 were locally isolated and morphologically classified as Podoviridae. While LKD16 adsorbs weakly to its host, LKA1 shows efficient adsorption (k = 3.9 x 10(-9) ml min). LKA1, however, displays a narrow host range on clinical P. aeruginosa strains compared to LKD16. Genome analysis of LKD16 (43,200 bp) and LKA1 (41,593 bp) revealed that both phages have linear double-stranded DNA genomes with direct terminal repeats of 428 and 298 bp and encode 54 and 56 genes, respectively. The majority of the predicted structural proteins were experimentally confirmed as part of the phage particle using mass spectrometry. Phage LKD16 is closely related to bacteriophage phi KMV (83% overall DNA homology), allowing a more thoughtful gene annotation of both genomes. In contrast, LKA1 is more distantly related, lacking significant DNA homology and showing protein similarity to phi KMV in 48% of its gene products. The early region of the LYA1 genome has diverged strongly from phi KMV and LKD16, and intriguing differences in tail fiber genes of LKD16 and LKA1 likely reflect the observed discrepancy in infection-related properties. Nonetheless, general genome organization is clearly conserved among phi KMV, LKD16, and LKA1. The three phages carry a single-subunit RNA polymerase gene adjacent to the structural genome region, a feature which distinguishes them from other members of the T7 supergroup. Therefore, we propose that phi KMV represents an independent and widespread group of lytic P. aeruginosa phages within the T7 supergroup.