Characterization of the novel bequatrovirus vB-BcgM and its antibacterial effects in a food matrix

Bacteria belonging to the Bacillus cereus group are ubiquitous in nature, causing food spoilage and food poisoning cases. A bequatrovirus, vB-BcgM, belonging to the C3 cluster infecting B. cereus group members, was isolated and characterized. Its 160-kb linear dsDNA genome contains a number of replication-related coding sequences (CDSs) and displays a collinear relationship with that of the virulent phage B4, with variations in its structural and replication regions. vB-BcgM has a relatively broad host range, with the ability to infect 33.3% of the B. cereus group isolates tested, including B. cereus, B. thuringiensis, B. anthracis, B. paranthracis, B. mycoides, and B. cytotoxicus. Moreover, vB-BcgM displays efficient infection and high replication capacity. It was found that 96.5% of the virions complete the adsorption process within 5 min. The optimal multiplicity of infection (MOI) is 10^-7, and the burst size is 63 plaque-forming units (PFU)/cell. This phage showed stability over a broad pH range (4-12) and at temperatures up to 70 °C. Furthermore, vB-BcgM displays significant antibacterial effects in processed food matrices (ultra-high temperature [UHT] sterilized milk [GB 25190], UHT refrigerated milk [GB 25190], pasteurized milk [GB 19645], mashed meat, and cereals) and fresh foods (lettuce, apple, and potato). The antibacterial effects were found to be dependent on the dose of viral inoculum, incubation conditions (food matrix and temperature), and time. The data indicate that vB-BcgM has good potential as an antibacterial agent.