Genomic and proteomic characterization of SE-I, a temperate bacteriophage infecting Erysipelothrix rhusiopathiae

A bacteriophage infecting pathogenic Erysipelothrix rhusiopathiae was isolated from a swine farm experiencing an outbreak of acute swine erysipelas; we designated this phage SE-I. SE-I has an icosahedral head, a long tail and a double-stranded DNA genome. The 34,997-bp genome has a GC content of 34 % and contains 43 open reading frames (ORFs) encoding packaging, structural, lysin-holin, and hypothetical proteins. Components of purified SE-I were separated using SDS-PAGE and analyzed using liquid chromatography–mass spectrometry. Nine proteins were identified, encoded by ORF9, ORF15, ORF23, ORF30, ORF31, ORF33, ORF39, ORF40 and ORF 42. A phylogenetic tree constructed based on the sequence of the large terminase subunit revealed that SE-I is closely related to Staphylococcus phages P954 and phi3396. The CHAP-domain-containing protein encoded by ORF25 was expressed in E. coli and which was able to inactivate host bacteria. SE-I was able to infect 7 of 13 E. rhusiopathiae strains, but was unable to infect Salmonella, Streptococcus suis, and Staphylococcus aureus. This is the first report of the isolation, characterization, and genomic and proteomic analysis of a temperate phage infecting E. rhusiopathiae, and it might lead to the development of new anti- E. rhusiopathiae agents.