Characterization and genomic analysis of a jumbo phage, PG216, with broad lytic activity against several Vibrio species

In this study, a lytic phage, named PG216, was obtained from seawater collected in Qingdao, using Vibrio parahaemolyticus strain G299 as its host. Transmission electron microscopy revealed that phage PG216 has an icosahedral head with a diameter of 100 ± 6.7 nm and a contractible tail with a length of 126 ± 6.7 nm. The spot assay and EOP assay for host range testing revealed that the phage displayed extensive lytic activity against five Vibrio species: V. alginolyticus, V. parahaemolyticus, V. vulnificus, V. mimicus, and V. harveyi. The one-step growth curve indicated that the phage has a latent period of 25 min, a lysis duration of 115 min, and an average burst size of 135 ± 02 PFU/cell. The genome of PG216 is 244,027 bp in length with a GC content of 42.89%, and itcontains383 ORFs and encodes 28 tRNAs. Phylogenetic analysis suggested that PG216 belongs to the genus Schizotequatrovirus within the family Straboviridae. Phage PG216 was found to be able to eradicate mature biofilms produced by V. parahaemolyticus G299. Phage PG216 demonstrates notable lytic activity while lacking virulence and antibiotic-resistance genes and therefore might be a viable candidate for use in phage therapy of vibriosis.