The PlyB endolysin of bacteriophage vB_BanS_Bcp1 exhibits broadspectrum bactericidal activity against Bacillus cereus sensu lato isolates

Abstract

Lytic bacteriophages (or phages) drive bacterial mortality by elaborating exquisite abilities to bind, breach, and destroy bacterial cell membranes and subjugate critical bacterial cell functions. These antimicrobial activities make phages ideal candidates to serve as, or provide sources of, biological control measures for bacterial pathogens. In this study, we isolated the Myoviridae phage vB_BanS_Bcp1 (here referred to as Bcp1) from landfill soil, using a Bacillus anthracis host. The antimicrobial activities of both Bcp1 and its encoded endolysin, PlyB, were examined across different B. cereus sensu lato group species, including B. cereus sensu stricto, Bacillus thuringiensis, and Bacillus anthracis, with pathogenic potential in humans and multiple different uses in biotechnological applications. The Bcp1 phage infected only a subset (11 to 66%) of each B. cereus sensu lato species group tested. In contrast, functional analysis of purified PlyB revealed a potent bacteriolytic activity against all B. cereus sensu lato isolates tested (n=79). PlyB was, furthermore, active across broad temperature, pH, and salt ranges, refractory to the development of resistance, bactericidal as a single agent, and synergistic with a second endolysin, PlyG. To confirm the potential for PlyB as an antimicrobial agent, we demonstrated the efficacy of a single intravenous treatment with PlyB alone or combination with PlyG in a murine model of lethal B. anthracis infection. Overall, our findings show exciting potential for the Bcp1 bacteriophage and the PlyB endolysin as potential new additions to the antimicrobial armamentarium.