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.