Yanmei Li,Lun Luo,Wenhai Wang,Bin Hong,Yi Ma,Jufang Wang
Synergistic antibacterial effect as a promising strategy against foodborne pathogens is compelling since the development of novel antibacterial agents is not so easy. Here we investigated the synergistic effect of cell wall hydrolase Lys14579 and cinnamaldehyde (CAL) against emetic Bacillus cereus . The MICs of Lys14579 and CAL against emetic B. cereus were 25 and 200 μg/mL, respectively. The combination of Lys14579 and CAL displayed a synergistic antimicrobial effect with a Fractional Inhibitory Concentration Index (FICI) of 0.375. Bactericidal assays revealed that this combination had better bactericidal performance than either substance alone. Furthermore, the combination of Lys14579 and CAL effectively inhibited the biofilm formation of emetic B. cereus at the concentrations of 6.25 and 50 μg/mL, respectively. Additionally, it down-regulated the cereulide synthetase gene ( cesB ) expression at the transcription level and reduced swarming motility by 55%. Scanning electron microscope and PI uptake assays further demonstrated that the combination accelerated the disruption of emetic B. cereus cells. Finally, the synergistic preservative effect of this combinational was observed in boiled rice and fresh lean beef. Thus, the combination of Lys14579 and CAL represents a potential synergistic strategy for controlling emetic B. cereus contamination in the food industry.
Yanmei Li,Lun Luo,Wenhai Wang,Bin Hong,Yi Ma,Jufang Wang
Bacillus cereus is a prevalent foodborne pathogen that induces food poisoning symptoms such as vomiting and diarrhea. Its capacity to form spores and biofilm enables it to withstand disinfectants and antimicrobials, leading to persistent contamination during food processing. Consequently, it is necessary to develop novel and efficient antimicrobial agents to control B. cereus , its spores, and biofilms. Peptidoglycan hydrolases have emerged as a promising and eco-friendly alternative owing to their specific lytic activity against pathogenic bacteria. Here, we identified and characterized a Lysozyme-like cell wall hydrolase Lys14579, from the genome of B. cereus ATCC 14579. Recombinant Lys14579 specifically lysed B. cereus without affecting other bacteria. Lys14579 exhibited strong lytic activity against B. cereus , effectively lysing B. cereus cell within 20 min at low concentration (10 μg/mL). It also inhibited the germination of B. cereus spores and prevented biofilm formation at 12.5 μg/mL. Moreover, Lys14579 displayed good antimicrobial stability with negligible hemolysis in mouse red blood cells and no cytotoxicity against RAW264.7 cells. Notably, Lys14579 effectively inhibited B. cereus in boiled rice and minced meat in a dose-dependent manner. Furthermore, bioinformatics analysis and point mutagenesis experiments revealed that Glu-47 was the catalytic site, and Asp-57, Gln-60, Ser-61 and Glu-63 were active-site residues related with the cell wall lytic activity. Taken together, Lys14579 could be a promising biocontrol agent against vegetative cells , spores, and biofilm of B. cereus in food industry.
危险品化学品经营许可证（带存储）