Abstract
Numerous reports have revealed that the bacterium Vibrio parahaemolyticus is responsible for significant economic losses in aquaculture and poses a threat to public health. In search of a sustainable biocontrol agent against V. parahaemolyticus, two lytic and novel bacteriophages, VpP1 and VpP2, were characterised. Both phages exhibited broad host ranges, lysing 13/16 V. parahaemolyticus strains. Phages were imaged by transmission electron microscopy, and analysis revealed that both phages exhibit morphology consistent with members of the class Caudoviricetes. Both phages inhibited the growth of their respective host bacterium with a high multiplicity of infection. All treated cultures had a substantial reduction in viability compared to non-treated cultures. One-step growth curve analysis revealed a latent period of approximately 22 min for both phages. The burst sizes were calculated as 10.2 PFU/mL, and 7.3 PFU/mL for VpP1 and VpP2, respectively. Stability determination assays revealed both phages could withstand a broad salinity range (1 to 20 %), pH levels (3.0-10.0), temperatures (-20 to 60 °C) and sodium hydrochlorite levels (3 to 10 mg/mL). Phages VpP1 and VpP2 could withstand direct UV light for 4 and 5 min, respectively. Next-generations sequencing revealed that VpP1 (63,510 bp) and VpP2 (64,298 bp) did not contain known virulence, antibiotic-resistance or lysogenic genes, highlighting their capability to be used as biocontrol agents. Phylogenetic analysis based on the major head protein revealed that VpP1 and VpP2 were categorised into the newly described Mardecavirus genus. The results suggest VpP1 and VpP2 have several beneficial qualities for future use as biocontrol agents. Further study is still required to determine their efficiency within food applications.