Isolation, characterization and genome analysis of the orphan phage Kintu infecting Xanthomonas vasicola pv. musacearum.

Background: Xanthomonas vasicola pv. musacearum is responsible for the widespread Banana Xanthomonas Wilt in banana cultivation regions across the globe. Biocontrol measures for disease management remain limited amidst increasing antimicrobial resistance and unsustainable conventional agricultural practices. The purpose of this study is to explore a viable alternative or adjunct strategy through the use of bacteriophages for disease management.

Results: Kintu was isolated from sewage and displayed clear and circular plaques measuring 3 mm. Based on transmission electron microscopy, Kintu displays siphovirus characteristics, including an icosahedral head and a non-contractile tail. Kintu infects 78% (22 out of 28) Ugandan Xvm strains, has an optimal multiplicity of infection of 1, a 10 min adsorption and latent period, a 35 min burst period, and a burst size of 15 particles per bacterium. Phage titers remain stable for two and half months (75 days) in SM buffer at -20 ^oC and - 40 ^oC but decrease significantly (p ≤ 0.0001) at 4 ^oC. Kintu is active at pH 3 and 11, maintains viability at temperatures between 25 ^oC and 120 ^oC and tolerates UV irradiation for up to 2 min and 20 s. Kintu inhibits Xvm growth at MOI ratios of 0.1, 1 and 10. The genome is a double stranded DNA molecule that consists of 48,985 base pairs and a G + C content of 51.71%. Antibiotic resistance genes or genes associated with a lysogenic life cycle are absent. There is limited sequence similarity of Kintu with other phages, making it a novel phage belonging to an unclassified genus of the class Caudoviricetes.

Conclusion: Kintu is a novel bacteriophage that infects and lyses Xanthomonas vasicola pv. musacearum, the causative agent for Banana Xanthomonas Wilt. Its stability across diverse temperatures and pH conditions highlights its potential as a biocontrol agent for managing the disease.