Genomic profile and infection dynamics of Kashi_RDG1 (KRDG1), a novel cluster K1 mycobacteriophage infecting mycobacterial hosts

Abstract

Introduction Tuberculosis (TB), caused by Mycobacterium tuberculosis, remains a major global health challenge, particularly due to the increasing emergence of multidrug-resistant strains and limited treatment options. Bacteriophages have gained attention as potential alternatives or adjuncts to conventional antibiotics owing to their host specificity and antibacterial efficacy. Methods This study reports the isolation and detailed characterization of mycobacteriophage Kashi_RDG1 (KRDG1), isolated using Mycobacterium smegmatis mc2155. Genomic analysis, transmission electron microscopy, host range analysis, one-step growth assay, adsorption assay, multiplicity of infection (MOI) determination, and infection kinetics were performed to characterize the phage. Results Genomic analysis identified KRDG1 as sub cluster K1 mycobacteriophage, with a genome size of 58,681 bp containing 95 predicted open reading frames (ORFs), of which 39 are functionally annotated. Transmission electron microscopy analysis confirmed its siphovirus-like morphology while host range analysis depicted its polyvalent activity against Mycobacterium fortuitum (opportunistic pathogen) and M. tuberculosis H37Ra (an attenuated Mtb strain) in addition to M. smegmatis. One-step growth analysis revealed latent period of 80 min and burst size of 100 phage/bacterial cell supporting its efficient infection dynamics. Notably, infection kinetics demonstrated strong host bacterial killing during the logarithmic phase. Discussion While KRDG1 exhibits temperate characteristics, its close genomic similarity to previously engineered therapeutic phage (ZoeJ) highlights its potential for future genetic engineering and therapeutic exploration against pathogenic mycobacterial and non-mycobacterial infections.