Yersiniophage ?R1-37 is a tailed bacteriophage having a 270?kb DNA genome with thymidine replaced by deoxyuridine

摘要

Bacteriophage ?R1-37 was isolated based on its ability to infect strain YeO3-R1, a virulence-plasmid-cured O antigen-negative derivative of Yersinia enterocolitica serotype O?:?3. In this study, the phage receptor was found to be a structure in the outer core hexasaccharide of Y. enterocolitica O?:?3 LPS. The phage receptor was present in the outer core of strains of many other Y. enterocolitica serotypes, but also in some Yersinia intermedia strains. Surprisingly, the receptor structure resided in the O antigen of Yersinia pseudotuberculosis O?:?9. Electron microscopy demonstrated that ?R1-37 particles have an icosahedral head of 88?nm, a short neck of 10?nm, a long contractile tail of 236?nm, and tail fibres of at least 86?nm. This implies that the phage belongs to the order Caudovirales and the family Myoviridae in the ICTV (International Committee for Taxonomy of Viruses) classification. ?R1-37 was found to have a lytic life cycle, with eclipse and latent periods of 40 and 50?min, respectively, and a burst size of ～80?p.f.u. per infected cell. Restriction digestions and PFGE showed that the ?R1-37 genome was dsDNA and ～270?kb in size. Enzymically hydrolysed DNA was subjected to HPLC-MS/MS analysis, which demonstrated that the ?R1-37 genome is composed of DNA in which thymidine (T) is 99?% replaced by deoxyuridine (dU). The only organisms known to have similar DNA are the Bacillus subtilis-specific bacteriophages PBS1 and PBS2. N-terminal amino acid sequences of four major structural proteins did not show any similarity to (viral) protein sequences in databases, indicating that close relatives of ?R1-37 have not yet been characterized. Genes for two of the structural proteins, p24 and p46, were identified from the partially sequenced ?R1-37 genome.