Isolation and Characterization of a Bacillus amyloliquefaciens Bacteriophage JBA6 and Its Endolysin PlyJBA6

Bacillus amyloliquefaciens is a Gram-positive, aerobic, spore-forming bacteria usually found in soil. Despite its probiotic potential, B. amyloliquefaciens has been identified as a cause of food spoilage, including the development of off-odors, rope formation, and the production of viscous substances in a wide range of foods. To control B. amyloliquefaciens, we isolated three B. amyloliquefaciens bacteriophages TBA3, JBA3, JBA6, and characterized one representative JBA6 endolysin, PlyJBA6. Transmission electron microscopy and genomic analysis demonstrated that all three phages belong to the Salasmaviridae family, characterized by short, non-contractile tails with linear dsDNA genomes ranging from 18.7 to 19.1 kb. PlyJBA6 contains a glycoside hydrolase family 24 domain (PF00959) at the N-terminus and two LysM domains (PF04176) at the C-terminus. While JBA6 has a narrow host range, infecting only 7 out of 9 tested strains of B. amyloliquefaciens, PlyJBA6 exhibits extended lytic range beyond the Bacillus genus. Interestingly, PlyJBA6 lyses Gram-negative bacteria such as Escherichia coli, Yersinia enterocolitica and Cronobacter sakazakii without other additives to destabilize bacterial outer membrane. We assume that JBA6 might be a useful component for a phage cocktail to control B. amyloliquefaciens and that PlyJBA6 can provide insights into the development of novel biocontrol agents against various food-borne pathogens.