Characterization and antibacterial modes of action of bacteriocins from Bacillus coagulans CGMCC 9951 against Listeria monocytogenes

Abstract

As one of the conventional probiotics, our previous findings have shown that Bacillus coagulans CGMCC 9951 had good antibacterial activity against various pathogenic bacteria. However, the action of the bacteriocins on antibacterial mode remained unclear. Based on the genomic DNA analysis of CGMCC 9951, two bacteriocins including Circularin A with 7736.14 Da and Amylocyclicin with 6371.57 Da were predicted and analyzed to simply simulate their structure. The crude bacteriocins mainly inhibited the growth of gram-positive bacteria, and the MIC against Listeria monocytogenes was 62.5 μg mL−1. The extracted bacteriocins showed good stability against pH, heat and surfactants, sensitivity to protease and weak hemolysis toxicity. The leakage of lactic dehydrogenase, nucleic acids and proteins, the bacterial uptake of propidium iodide, the observation of bacterial cell integrity, and gel retardation of genomic DNA demonstrated that the bacteriocins can destroy firstly cell membrane due to the presence of pore, and then lead to the leakage of cell contents and the inactivation of genomic DNA, affecting finally the normal growth and reproduction of indicator bacteria. The discovery of the bacteriocins and the investigation of antibacterial mechanism were expected to contribute to the development of a natural food preservative for the application of food industry.