Characterization and complete genomic analysis of a novel broad host-range Escherichia coli phage isolated from Marmota himalayana

Abstract:

[Objective] To isolate and characterize the bacteriophage from the intestinal contents of Marmota himalayan.[Methods]A lytic phage was isolated from the host Escherichia coli in intestinal contents of M.himalayan with the double-layer agar method.The morphological characteristics were observed by transmission electron microscopy (TEM).Meanwhile,the optimal multiplicity of infection (MOI),one-step growth curve,pH stability,and the host range of the phage were investigated,and the genome was analyzed as well.[Results] The lytic bacteriophage was named vB_EcoM_TH18 and the phage plaque was transparent and round with a clear boundary.According to TEM,the phage had the head of (90±5) nm in diameter and tail of (115±5) nm in length.The optimal MOI was 1.According to the one-step growth curve,vB_EcoM_TH18 had a latent period of 20 min and the lysis period of about 110 min with the average burst size of about 15 PFU/mL.vB_EcoM_TH18 can keep stable titer at pH 4.5-9.5.Additionally,it can lyse various pathotypes and serotypes of E.coli and Shigella sonnei,while Salmonella,Enterococcus faecium,Staphylococcus aureus,Klebsiella pneumonia,and Acinetobacter baumannii can't be lysed.The genome of the vB_EcoM_TH18 was 133 882 bp with the G+C content of 39.95%.It comprised 210 coding sequences (CDS) and 13 tRNAs genes,without any virulence genes or antibiotic-resistant genes.BLASTn alignment showed that genome of vB_EcoM_TH18 shared 95.17% identity to E.coli phage Av-05.According to the polygenetic trees for the whole genomes,major capsid proteins,and terminase large subunits of vB_EcoM_TH18 and otherMyoviridae phages,respectively,vB_EcoM_TH18 was a novel phage in Avunavirus of Myoviridae.[Conclusion] In this study,we isolated and identified a novel broad host-range E.coli phage vB_EcoM_TH18.It can lyse various pathotypes and serotypes E.coli and S.sonnei.