Characterization of a newly isolated Dhillonvirus bacteriophage vB_EcoS-UDS3lw against Escherichia coli O157:H7

Abstract Objective The aim of this study is to characterize a new Dhillonvirus bacteriophage that is lytic against E. coli strains, particularly E. coli O157:H7. Methods used for characterization included bacteriophage isolation, purification, bacteriophage morphology, host range test, one-step growth curve, whole-genome sequencing and analysis, and preliminary determination of depolymerase activity. Results The complete genome sequence of Escherichia phage vB EcoS UDS3lw consists of double-stranded DNA, with a genome length of 44,071 base pairs and GC content of 54.67%. UDS3lw did not contain bacterial virulence genes, such as stx , or lysogenic genes in the phage genome. The phylogenetic analysis at the nucleotide level revealed that UDS3lw shared a close evolutionary relationship with Escherichia phages SM S22 and SSL-2009a, belonging to the Dhillonvirus genus. UDS3lw has a narrow host spectrum against E. coli O157:H7 and some non-pathogenic E. coli strains. Despite a small burst size of 2.4 PFU/cell on E. coli O157:H7 (RM9995), UDS3lw encodes a tail fiber protein (ORF 31) with depolymerase activity against non-pathogenic E. coli and most E. coli O157 strains. The findings provide insights into the genetic and biological diversity of the E. coli- infecting phage UDS3lw, which exhibits depolymerase activity and holds promise for further development as an anti-biofilm agent.