Characterization of an endolysin from B. cereus-infecting bacteriophage B13S and its application as antimicrobial and detection agents

Bacillus cereus is a ubiquitous bacterium responsible for food poisoning. To control B. cereus, a novel B. cereus-specific bacteriophage, B13S, was isolated, and its endolysin (PlyB13S) was characterized. B13S has 155.77-kb double-stranded DNA containing 222 open reading frames. B13S infects only 2 of the 24 B. cereus strains; however, its host strains are not killed by other phages, supporting its novelty. PlyB13S possesses a conserved N-terminal glycoside hydrolase domain; however, there was no match for the C-terminal region in the conserved domain database. PlyB13S rapidly lysed bacterial cells and showed a much broader lytic spectrum than the parental phage. In addition, PlyB13S removed B. cereus biofilms and reduced the viable B. cereus cells in boiled rice by 2 log CFU/mL. This potent antimicrobial activity may be due to the cell wall-binding domain of PlyB13S, which specifically binds to 12 strains of B. cereus in buffer and shows strong binding activity in sterilized milk. Interestingly, the enzymatic active domain of PlyB13S showed weaker lytic activity than the full-length endolysin toward B. cereus, but rapidly lysed Geobacillus stearothermophilus cells and eliminated their biofilms. These results suggest that PlyB13S and its domains could be used as novel diagnostic and biocontrol tools.