Novel Escherichia coli Phages Representing a Distinct Genus within Stephanstirmvirinae: Genome and Host Range Characteristics

Bacteriophages play crucial roles in microbial ecosystems and have potential biotechnological applications. However, our understanding of culturable phages remains limited. This study characterized six novel Escherichia coli phages isolated from pig farm wastewater and urban sewage using comprehensive genomic, morphological, and host-range analyses. Using multiple comparative approaches, including gene-sharing network analysis, average nucleotide identity (ANI), and nucleotide intergenomic similarity (NIS), we demonstrated that five of these phages form a distinct group within the subfamily Stephanstirmvirinae , potentially representing a novel genus provisionally named " Wecvirus ”. These phages were further classified into two distinct species within the proposed genus, each of which exhibits a unique host range pattern. This host specificity is reflected in the species-specific differences in the amino acid sequences of tail fibers, which are crucial for infection. The remaining phage, which was not classified as Wecvirus exhibited characteristics that challenged the current classification criteria, highlighting the need for more flexible taxonomic approaches. Our findings expand the understanding of phage diversity within Stephanstirmvirinae and contribute to the evolving phage taxonomy framework. Importance The rapid emergence of antibiotic-resistant pathogens necessitates the development of alternative antimicrobial strategies, with phage therapy showing promising potential. However, the successful implementation of phage-based treatments requires a comprehensive understanding of phage diversity and host-pathogen interactions. Our study expands the known diversity within Stephanstirmvirinae by characterizing novel E. coli phages that constitute a distinct genus. The identification of species-specific host recognition mechanisms within this genus provides insights into phage-host adaptation. These findings contribute to our understanding of phage taxonomy and evolution, while also offering practical implications for the development of phage-based therapeutics against pathogenic E. coli strains. This research highlights the importance of continued exploration of novel phages for both fundamental understanding and therapeutic applications.