Characterization of virulent bacteriophages targeting Bacillus licheniformis: biological properties and genomic functional analysis

The growth of spore-forming bacteria from the Bacillus genus, which negatively impacts food quality, remains a significant problem, leading to considerable economic losses in production facilities. Therefore, this study reports the isolation and characterization of bacteriophages targeting Bacillus licheniformis as a potential candidate for food biocontrol. Biological assessments showed that Bacillus phage KKP_4048 and Bacillus phage KKP_4049 are highly stable under various environmental conditions. The phages retained activity across a broad temperature range (−20 °C–60 °C for 1 h) and in saline solutions with pH values from 3 to 11 for 1 h. After 30-min of UV exposure, their activity decreased by 99.99 %. Transmission electron microscopy revealed that Bacillus phage KKP_4048 and Bacillus phage KKP_4049 belong to the Caudoviricetes class with a myovirus morphotype. The growth kinetics of the bacteriophage's host were examined using an automated growth analyzer, demonstrating a significant reduction in host growth at all tested multiplicity of infections. The genomes of Bacillus phage KKP_4048 and Bacillus phage KKP_4049 consist of linear dsDNA, with a length of 152,106 bp and 154,029 bp, and G + C contents of 39.01 % and 38.97 %, respectively. Phylogenetic analysis showed that phages are most closely related to bacteriophages in the Herelleviridae family and the Siophivirus genus. No lysogenic markers, including genes for toxins or antibiotic resistance, were detected in their genomes. These results suggest that Bacillus phage KKP_4048 and Bacillus phage KKP_4049 hold significant potential as a biocontrol agent for food safety.