Genomic Characterization of Sixteen Yersinia enterocolitica-Infecting Podoviruses of Pig Origin.

Yersinia enterocolitica causes enteric infections in humans and animals. Human infections are often caused by contaminated pork meat. Y. enterocolitica colonizes pig tonsils and pigs secrete both the human pathogen and its specific bacteriophages into the stools. In this work, sixteen Y. enterocolitica -infecting lytic bacteriophages isolated from pig stools originating from several pig farms were characterized. All phages belong to the Podoviridae family and their genomes range between 38,391-40,451 bp in size. The overall genome organization of all the phages resembled that of T7-like phages, having 3-6 host RNA polymerase (RNAP)-specific promoters at the beginning of the genomes and 11-13 phage RNAP-specific promoters as well as 3-5 rho-independent terminators, scattered throughout the genomes. Using a ligation-based approach, the physical termini of the genomes containing direct terminal repeats of 190-224 bp were established. No genes associated with lysogeny nor any toxin, virulence factor or antibiotic resistance genes were present in the genomes. Even though the phages had been isolated from different pig farms the nucleotide sequences of their genomes were 90-97% identical suggesting that the phages were undergoing microevolution within and between the farms. Lipopolysaccharide was found to be the surface receptor of all but one of the phages. The phages are classified as new species within the T7virus genus of Autographivirinae subfamily.