Biological characteristics and genomic study of two Vibrio alginolyticus phages

Vibrio alginolyticus, as a significant pathogen causing highly virulent bacterial diseases in the culture of Babylonia areolata, poses a great challenge to the environment and public health due to the emergence of its drug-resistant strains. In this study, two phages, vB_VapS_BA4 and vB_VapS_BA30, were isolated and identified using V. alginolyticus as the host bacterium. Using techniques such as electron microscopy, biological tests, and genomic analysis, we identified their classification, lytic features, and environmental stability. The results show that phage vB_VapS_BA4 belongs to the genus Vasivirus within the family Inoviridae, with a circular single-stranded DNA (ssDNA) genome. This phage has a latent period ranging from 0 to 20 min and a burst size up to 523.38 PFU/cell, indicating strong antibacterial activity. vB_VapS_BA30 is identified as a new member of the class Caudoviricetes, containing a circular double-stranded DNA (dsDNA) genome with unique genomic features. It has a latent period of less than 10 min and a burst size of 32.97 PFU/cell. Both phages can withstand pH levels from 2 to 12 and temperatures between 4 and 65 °C, showing high environmental adaptability. Additionally, genomic analysis revealed no antibiotic resistance genes or virulence factors, suggesting a safe profile. This study offers a theoretical basis and practical insights for developing innovative phage-based control methods that could reduce antibiotic use, lower the risk of resistance, and support sustainable progress in aquaculture.