Isolation and characterization of an efficient lytic T1-like phage against Escherichia coli

Abstract:

[Objective] Bacteriophages are recognized as the most abundant microorganisms on earth, and have potential to control antibiotic-resistant bacterial infections for their bactericidal activity. Bacteriophages display remarkable genetic diversity and host specificity. To determine the biological characteristics and sequences of an efficient lytic Escherichia coli phage isolated from swine intestines. [Methods] Potential phages in the samples from piglet intestinal contents were isolated and purified, and plaque characteristics of the phage were observed. Morphological analysis was performed by electron microscope. The host spectrum, multiplicity of infection, one-step growth curve, thermal stability, pH stability, sensitivity to ultraviolet and chloroform sensitivity were determined, and genomic evolution was analyzed. [Results] A new lytic Escherichia coli phage, named vB_EcoS_SH2 (SH2), was isolated. The phage plaque was shown as big, circular, transparent and neat. Morphological analysis by electron microscopy revealed that phage SH2 had an icosahedron head with 50 nm in diameter, and a systolic tail fiber with 8 nm width and 120 nm length. Phage SH2 had a short latent period of 10 min and an outbreak period of 60 min, and a burst size of 121 PFU/infected cell. The optimal MOI is 0.1. Genome sequencing and comparison revealed that the nucleic acid type of SH2 is dsDNA, and the DNA genome of SH2 is composed of 49 088 bp with a G+C% content of 45% (GenBank accession number: KY985004). Phage morphology and BLASTp analysis revealed that SH2 belongs to the family of Caudovirales, Siphoviridae. Genomic and phylogenetic analysis suggested that the phage is closely related to phage T1, with 95% homology to T1 phage. [Conclusion] a novel efficient lytic T1-like phage vB_EcoS_SH2 against Escherichia coli was identified. The microbiological properties of SH2 suggest that it may be useful for controlling bacterial populations.