Characterization of a temperate bacteriophage vB_Eco_ppH1 induced from Escherichia coli ST131 lineage

Abstract Escherichia coli is a major commensal and opportunistic pathogen inhabiting the gastrointestinal tract of warm-blooded animals, including marine mammals. Among its lineages, sequence type 131 (ST131) is a globally disseminated high-risk clone associated with severe infections. Prophages are common in intestinal bacteria, and their induction has been hypothesized to influence bacterial population dynamics and gut homeostasis. However, experimentally characterized temperate phages derived from E. coli ST131 strains remain limited. Here, we characterized vB_Eco_ppH1, a temperate phage induced from a marine mammal-derived ST131 E. coli strain. Transmission electron microscopy revealed a siphovirus-like morphology. The phage exhibited bacteriolytic activity against the indicator host, E. coli C, reduced the biomass of preformed E. coli biofilms, and retained detectable infectivity after exposure to a range of tested pH and temperature conditions. Genomic analysis revealed that the induced phage possessed a dsDNA genome (47,573 bp) encoding 66 predicted open reading frames. Genome-wide phylogenetic and intergenomic similarity analyses classified vB_Eco_ppH1 within the subfamily Jacobvirinae and genus Bievrevirus . Its highest intergenomic similarity to a classified relative was 77.6%, below the 95% species demarcation threshold, supporting its designation as a putative novel species within Bievrevirus . This study provides a biological and genomic characterization of an inducible temperate phage derived from a lysogenic E. coli ST131 strain and expands the experimental knowledge of temperate phages associated with this clinically important lineage.