Synthetic plantaricins show significantly enhanced antibacterial activity against Flavobacterium sp.

The culture supernatant of Lactiplantibacillus plantarum KM2 exhibited antimicrobial activity against seven foodborne pathogens. Genomic analysis revealed the presence of an operon capable of producing plantaricins, specifically bacteriocins known as plantaricins A, E, F, J, and K. In this study, genomic comparisons confirmed that this plantaricin operon was strain-specific to L. plantarum rather than universally present in all strains of the species. Genes corresponding to plantaricins A, E, F, J, and K were identified and their syntheses confirmed, leading to the verification of their antimicrobial activities. Synthesized plantaricins were prepared individually and in combinations of two or three. Their antimicrobial activities were tested against nine indicator strains. The results showed variations in the magnitude and efficacy of their antimicrobial activity, depending on the combination used. Among them, the combination of synthesized plantaricins spPlnAEJ and spPlnAEK showed the greatest effect against Flavobacterium sp. KCCM 11374. To elucidate the mechanism of antimicrobial activity, Raman spectra were examined. Notably, the Raman spectra of Flavobacterium sp. KCCM 11374 treated with synthesized plantaricins differed quite a bit from the untreated spectra, suggesting a distinct effect. Additionally, transmission electron microscopy results revealed that these synthesized plantaricins could induce the cell lysis of Flavobacterium sp. KCCM 11374.