Abstract:
Objective A Yersinia pestis phage from a Himalayan marmot was isolated and identified, and its basic biological characteristics and genomics characteristics were analyzed.
Methods The cecum specimens of Marmota himalayan, a host animal in the natural focus of pestis, were collected, and the Yersinia pestis vaccine strain EV76 was used as the host bacteria to isolate and purify the phage. The morphology of the phage was observed by transmission electron microscopy, and its biological characteristics were studied. The DNA of the pestis phage was extracted for second-generation sequencing, and its genome characteristics and functions were analyzed by bioinformatics software.
Results The phage named vB_YpM_QH041 was isolated from the cecum of a Himalayan marmot from natural plague focus belonged to Myoviridae with a icosahedral structure and a typical retractable tail. Studies on the biological characteristics showed that the multiplicity of infection was 0.1, the latent period was 40 minutes, the outbreak period was about 40 minutes, and the burst size was 10 PFU/cell（plaque forming unit, PFU). The bacteriophage cracked all the 33 strains in the 10 natural focus of pestis tested, and cracked one Yersinia pseudotuberculosis in the genus Yersinia; It has lytic activity against a non-pathogenic Escherichia coli (MG1655) strain within the Enterobacteriaceae family, but does not have significant lytic activity against other Escherichia coli, Salmonella, or Shigella strains. The genome length of this phage was 31940 bp, with a GC content of 51.52%. There are 42 open reading frames, with a total length of 28.99 k, of which 35 are known coding sequences. No virulence genes or antibiotic resistance genes are present. The result of homology analysis of the phylogenetic tree of the whole genome of the bacteriophage shows that this bacteriophage and the pestis bacteriophage vB_YpM_22 and VB_YPM_18 are closely related and belong to the P2 phage group.
Conclusion This phage vB_YpM_QH041 has good lytic ability to Yersinia pestis and can also lyse other intestinal bacteria, which is helpful for us to understand the preservation problem of Yersinia pestis in the natural foci.
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