PhPV1.2, a novel Autographivirales bacteriophage infecting biofilm forming Vibrio parahaemolyticus: genomic insights and characterization

Vibrio parahaemolyticus , a Gram-negative, halophilic bacterium, is a common causative agent of gastroenteritis linked to the consumption of undercooked or raw seafood. The growing prevalence of bacterial strains, including that of V. parahaemolyticus , has raised serious concerns and has evoked interest in alternative solutions, such as the use of lytic bacteriophages for phage therapy. In this study, we report the isolation of a biofilm forming, V. parahaemolyticus strain PV1.2 and its specific lytic bacteriophage, designated PhPV1.2, from a tidal pool in Puthuvype, Kochi, located on the southwest coast of India. Transmission electron microscopy (TEM) analysis revealed that PhPV1.2 possesses an icosahedral capsid, 53 ± 5 nm in diameter with a very short non-contractile tail. One-step growth curve analysis indicated a latent period of 105 min and a burst size of 60 plaque-forming units (pfu) per infected cell. The adsorption constant of the phage was estimated as 4.6 × 10 − 9 mL min − 1 . PhPV1.2 demonstrated thermal stability up to 76 ℃ and retained infectivity across a pH range of 5 to 11, however, its viability declined markedly at temperatures above 70 ℃ and at extreme pH values (< 3 or > 11). Whole genome sequencing using an Illumina 2 × 150 bp paired end approach followed by de novo assembly revealed a 42.5 kbp dsDNA genome with a G + C content of 47.79%, housing 61 predicted protein-encoding open reading frames (ORFs). Comprehensive genomic characterization and comparative analyses, including phylogeny based on conserved marker genes and whole genome, proteomic clustering using ViPTree, and average nucleotide identity (ANI) as well as intergenomic similarity assessments, identified PhPV1.2 as a novel species within the order Autographivirales (class Caudoviricetes ). The complete genome sequence of PhPV1.2 has been deposited in the NCBI GenBank database under the Accession no. PQ511476.