Controlling pepper soft rot by Lactobacillus paracasei WX322 and identification of multiple bacteriocins by complete genome sequencing

Bacterial soft rot is a devastating disease that harms vegetables. Lactic acid bacteria (LAB) can be effective antagonist against soft rot pathogens. In this study, Lactobacillus paracasei WX322 and its produced bacteriocin had antibacterial activities against a variety of foodborne pathogens and spoilage bacteria, including both Gram-positive and Gram-negative bacteria, especially the soft rot pathogen Pectobacterium carotovorum subsp. brasiliense BZA12 (Pcb BZA12). The in vivo antibacterial test proved that the bacteriocin produced by the L. paracasei WX322 could control soft rot disease of peppers caused by Pcb BZA12. The L. paracasei WX322 produced bacteriocin after fermentation for 36 h, which had broad antimicrobial activity. In addition, the bacteriocin produced by L. paracasei WX322 had good thermal stability and broad pH adaptation. Then, the complete genome of L. paracasei WX322 was sequenced with one circular chromosome and eight plasmids. Three bacteriocin gene clusters were identified in the genome by antiSMASH. Furthermore, seven genes in the three gene clusters were identified to be bacteriocins. Moreover, three of the seven bacteriocins were novel. The complete genome sequences of the L. paracasei WX322 can provide a better molecular basis of its antibacterial activity and biocontrol effect on bacterial soft rot disease.