Background: Bacillus cereus is a foodborne pathogen that causes emetic or diarrheal types of food poisoning. The\r\nincidence of B. cereus food poisoning has been gradually increasing over the past few years, therefore, biocontrol\r\nagents effective against B. cereus need to be developed. Endolysins are phage-encoded bacterial peptidoglycan\r\nhydrolases and have received considerable attention as promising antibacterial agents.\r\nResults: The endolysin from B. cereus phage B4, designated LysB4, was identified and characterized. In silico\r\nanalysis revealed that this endolysin had the VanY domain at the N terminus as the catalytic domain, and the\r\nSH3_5 domain at the C terminus that appears to be the cell wall binding domain. Biochemical characterization of\r\nLysB4 enzymatic activity showed that it had optimal peptidoglycan hydrolase activity at pH 8.0-10.0 and 50�°C. The\r\nlytic activity was dependent on divalent metal ions, especially Zn2. The antimicrobial spectrum was relatively\r\nbroad because LysB4 lysed Gram-positive bacteria such as B. cereus, Bacillus subtilis and Listeria monocytogenes and\r\nsome Gram-negative bacteria when treated with EDTA. LC-MS analysis of the cell wall cleavage products showed\r\nthat LysB4 was an L-alanoyl-D-glutamate endopeptidase, making LysB4 the first characterized endopeptidase of this\r\ntype to target B. cereus.\r\nConclusions: LysB4 is believed to be the first reported L-alanoyl-D-glutamate endopeptidase from B. cereusinfecting\r\nbacteriophages. The properties of LysB4 showed that this endolysin has strong lytic activity against a\r\nbroad range of pathogenic bacteria, which makes LysB4 a good candidate as a biocontrol agent against B. cereus\r\nand other pathogenic bacteria.
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