Isolation and Genome Characterization of Escherichia Phage vB_EcoA-Sparklingdew

Escherichia coli remains a critical multidrug-resistant nosocomial pathogen, driving interest in bacteriophage-based biocontrol. The genus Kayfunavirus (family Autotranscriptaviridae) exhibits obligately lytic replication cycles and favorable biosafety profiles, yet each new phage requires comprehensive genomic characterization to expand therapeutic candidate pools. This study aimed to isolate and genomically characterize a novel Kayfunavirus from an environmental reservoir in Vietnam.

Escherichia phage vB_EcoA-Sparklingdew was isolated from Can Tho River water using host E. coli AgE9. The genome was assembled using SPAdes. The termini were resolved with PhageTerm. The annotation was done via the Pharokka pipeline and HHpred. Taxonomic classification was performed using taxMyPhage, VIRIDIC intergenomic comparisons, and maximum likelihood phylogeny of concatenated structural proteins.

The complete genome comprises a 37,944 bp linear dsDNA molecule (49.9% GC), encoding 51 open reading frames in a predominantly unidirectional arrangement. Key features include a virion-encoded T7-like RNA polymerase, a 723-residue T7-like DNA polymerase, a canonical lysis triad, and two putative tailspike proteins. A 212 bp direct terminal repeat and coverage profiles support a headful (pac) packaging mechanism. Comprehensive screening confirmed the absence of lysogeny, virulence, and antibiotic resistance determinants. A single synonymous SNP indicated high clonal purity. Intergenomic identity peaked at 87.7% against ICTV references, confirming placement in a novel species.

Phage Sparklingdew represents a strictly lytic Kayfunavirus with a compact genomic architecture. Its favorable safety profile and absence of temperate markers support further evaluation for targeted therapeutic applications against pathogenic E. coli.