Abstract: 【Objective】 The experiment aimed to screen out a bacteriocin of lactic acid bacteria agaist Pasteurella multocida,complete the whole genome sequencing of the isolated lactic acid bacteria,and analyze the physicochemical properties and bactericidal mechanism of its bacteriocin. 【Method】 Healthy cat feces were inoculated in MRS broth medium and cultured at 37 ℃ for 12 h to isolate bacteria.With Pasteurella multocida as the indicator bacteria,the antibacterial activity of the isolated lactic acid bacteria was determined by Oxford cup agar diffusion method and the isolated lactic acid bacteria were identified by amplifying 16S rRNA gene.The whole genome sequence was determined and annotated in the KEGG database.The biological characteristics of the antibacterial substances produced by the isolated bacteria were determined using protease sensitivity,thermal stability and acid-base stability tests.The antibacterial properties of antibacterial substances were explored by using scanning electron microscopy technology. 【Result】 One strain of lactic acid bacteria producing antibacterial substances was screened out.Morphological observation showed that the surface of the colony was smooth and the morphology was small.Gram staining showed positive cocci.16S rRNA sequencing analysis showed that the similarity between the isolated strain and Weisseria confusa was 97%,and it was identified as Weisseria confusa,named JLP1.The results of whole genome sequencing showed that the genome size of Weisseria confusa JLP1 was 2 350 892 bp,with an effective average GC content of 44.94% and 2 020 coding genes.There were a total of 1 051 genes annotated in the KEGG database,which were the three major functions of environmental information processing,metabolism,and genetic information processing systems,with a total of 49 metabolic pathways.The results of acid excretion and hydrogen peroxide excretion test showed that the antibacterial substance of Weisseria confusa JLP1 was not organic acid and hydrogen peroxide,and the antibacterial activity decreased significantly after proteinase K treatment,so it was presumed that the antibacterial substance was bacteriocin.The antibacterial activity of bacteriocin produced by Weisseria confusa JLP1 was stable within 40 to 80 ℃,and did not lose activity after 10 minutes of treatment at 100 ℃,which had good thermal stability.It had good antibacterial activity within pH 3.0-8.0 and a wide range of acid-base tolerance.The scanning results of the electron microscope showed that the bacteriocin produced by Weisseria confusa JLP1 attacked the cell membrane of Pasteurella multocida,forming pores and causing the cell surface to shrink. 【Conclusion】 Weisseria confusa JLP1 had many metabolism and amino acid biosynthesis genes,and the bacteriocin produced by the strain had stable physicochemical properties and good antibacterial effect,providing a beneficial reference for preventing Pasteurella multocida infection.

Key words: Pasteurella multocida; whole genome sequencing; bacteriocin