Abstract:By using different Gram-positive bacteria(Staphylococcus aureus, Bacillus cereus, Lactobacillus plantanrum) and Gram-negative bacteria (Citrobacter freundii, Vibrio parahemolyticus, Escherichia coli, Salmonella enterica, Shigella flexneri) as indicator strains, some collection of bacterial strains isolated from the oysters of Xiapu Sea in Fujian province were screened for bacteriocin producers with broad inhibition spectra. All the fourteen strains with broad-spectrum inhibitory effect were initially identified as Bacillus sp. by morphological characteristics and 16s rDNA analysis. The bacteriocins produced by the Bacillus sp. are characterized by strong thermal stability and easy-decomposition by protease. The range of inhibition spectrum and the results of repeated fragment gene fingerprinting(rep-PCR) showed that the 14 strains of Bacillus could be further divided into four Bacillus strains with different genotypes for subsequent experiments. It was found from the plasmid extraction results that the bacteriocins producing by four strains of Bacillus sp. were synthesized by chromosome coding. The crude bacteriocins extracted by ammonium sulfate method and gel filtration chromatography still showed strong antibacterial activity. The Tricine-SDS-PAGE electrophoresis results showed that the molecular weights of bacteriocins producing by the four Bacillus strains were all less than 20 ku, which can be classified as Class II bacteriocins from lactic acid bacteria. Combined with the comparisons and identification of LC-MS/MS, no related well-known bacteriocins were found in the database, indicating that the four strains of Bacillus may produce novel broad-spectrum bacteriocins.