Characterization of Giant Myoviridae With Therapeutic Potential Against Grouper Pathogen, Vibrio alginolyticus

Background: Vibrio alginolyticus is a gram-negative bacterium responsible for mass mortality in cultured groupers, leading to significant economic losses in the aquaculture industry. Although preventive measures such as chemical treatments, antibiotics, and pesticides have been employed, these methods have been reported to be toxic to the environment and contribute to the development of antimicrobial resistance (AMR) in treated fish. Methods: In this study, a giant Myoviridae phage strain (ValKK1-20) was isolated from the sandy area of Kota Kinabalu, Sabah, Malaysia. The purified phage was characterized based on transmission electron microscopy (TEM) and its genomic DNA. The adsorption assay and one-step growth analyses were conducted to predict the critical phase of ValKK3 infection. Results: TEM analysis revealed that the phage possessed an elongated head with a sheathed tail, resembling members of the T4-like Myoviridae group. The genome characterization revealed that the phage belongs to T4 phage with a genome size 248,088 bp with 41.2% G + C content and 390 predicted open reading frames. Additionally, it demonstrated a short eclipse period of 36 min and a latent period of 48 min, with a large burst size of approximately 174 plaque-forming units (PFU) per cell. Conclusions: In conclusion, this study highlights the potential of selected phage ValKK3 as a biocontrol agent against V. alginolyticus, offering a promising alternative for sustainable aquaculture management.