Genomic analysis and biological characterization of a novel Schitoviridae phage infecting Vibrio alginolyticus

Vibrio alginolyticus is a Gram-negative bacterium commonly associated with mackerel poisoning. A bacteriophage that specifically targets and lyres this bacterium could be employed as a biocontrol agent for treating the bacterial infection or improving the shelf-life of mackerel products. However, only a few well-characterized V. alginolyticus phages have been reported in the literature. In this study, a novel lytic phage, named Phi ImVa-1, specifically infecting V. alginolyticus strain ATCC 17749, was isolated from Indian mackerel. The phage has a short latent period of 15 min and a burst size of approximately 66 particles per infected bacterium. Phi ImVa-1 remained stable for 2 h at a wide temperature (27-75 degrees C) and within a pH range of 5 to 10. Transmission electron microscopy revealed that Phi ImVa-1 has an icosahedral head of approximately 60 nm in diameter with a short tail, resembling those in the Schitoviridae family. High throughput sequencing and bioinformatics analysis elucidated that Phi ImVa-1 has a linear dsDNA genome of 77,479 base pairs (bp), with a G+C content of similar to 38.72% and 110 predicted gene coding regions (106 open reading frames and four tRNAs). The genome contains an extremely large virion-associated RNA polymerase gene and two smaller non-virion-associated RNA polymerase genes, which are hallmarks of schitoviruses. No antibiotic genes were found in the (13ImVa-1 genome. This is the first paper describing the biological properties, morphology, and the complete genome of a V. alginolyticus-infecting schitovirus. When raw mackerel fish flesh slices were treated with Phi ImVa-1, the pathogen loads reduced significantly, demonstrating the potential of the phage as a biocontrol agent for V. alginolyticus strain ATCC 17749 in the food.

Automated summary

In this study, a novel lytic phage, named Phi ImVa-1, specifically infecting V. alginolyticus strain ATCC 17749, was isolated from Indian mackerel. The phage has a short latent period and a large burst size, and remains stable at a wide range of temperature and pH. The genome analysis revealed that Phi ImVa-1 belongs to the Schitoviridae family. It was also found that the use of Phi ImVa-1 can significantly reduce the infection of V. alginolyticus strain ATCC 17749 in food.