| Summary: | <p>Abstract</p> <p>Background</p> <p><it>Bacillus cereus </it>is a foodborne pathogen that causes emetic or diarrheal types of food poisoning. The incidence of <it>B. cereus </it>food poisoning has been gradually increasing over the past few years, therefore, biocontrol agents effective against <it>B. cereus </it>need to be developed. Endolysins are phage-encoded bacterial peptidoglycan hydrolases and have received considerable attention as promising antibacterial agents.</p> <p>Results</p> <p>The endolysin from <it>B. cereus </it>phage B4, designated LysB4, was identified and characterized. <it>In silico </it>analysis revealed that this endolysin had the VanY domain at the N terminus as the catalytic domain, and the SH3_5 domain at the C terminus that appears to be the cell wall binding domain. Biochemical characterization of LysB4 enzymatic activity showed that it had optimal peptidoglycan hydrolase activity at pH 8.0-10.0 and 50°C. The lytic activity was dependent on divalent metal ions, especially Zn<sup>2+</sup>. The antimicrobial spectrum was relatively broad because LysB4 lysed Gram-positive bacteria such as <it>B. cereus, Bacillus subtilis </it>and <it>Listeria monocytogenes </it>and some Gram-negative bacteria when treated with EDTA. LC-MS analysis of the cell wall cleavage products showed that LysB4 was an <smcaps>L</smcaps>-alanoyl-<smcaps>D</smcaps>-glutamate endopeptidase, making LysB4 the first characterized endopeptidase of this type to target <it>B. cereus</it>.</p> <p>Conclusions</p> <p>LysB4 is believed to be the first reported <smcaps>L</smcaps>-alanoyl-<smcaps>D</smcaps>-glutamate endopeptidase from <it>B. cereus</it>-infecting bacteriophages. The properties of LysB4 showed that this endolysin has strong lytic activity against a broad range of pathogenic bacteria, which makes LysB4 a good candidate as a biocontrol agent against <it>B. cereus </it>and other pathogenic bacteria.</p>
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