Antibacterial mechanism of metabolites of Leuconostoc mesenteroides against Serratia liquefaciens

The antibacterial mechanism of metabolites of Leuconostoc mesenteroides SCB2557 (MLm SCB2557) against Serratia liquefaciens (S. liquefaciens) was investigated in this study by determining the growth curve, biofilm formation, cell integrity and cell morphology of S. liquefaciens, as well as the antibacterial components of MLm SCB2557. The results showed that MLm SCB2557 was able to effectively inhibit the growth and biofilm formation of S. liquefaciens. A remarkable increase in extracellular AKPase and fluorescence of propidium iodide (PI) in S. liquefaciens cells was found after MLm SCB2557 treatment, indicating disruption of cell wall and cell membrane integrity, respectively. The results of cell morphology by field emission scanning electron microscopy (FESEM) showed that S. liquefaciens cells were broken and distorted in shape after MLm SCB2557 treatments at higher concentrations. Furthermore, it was confirmed that the inhibitory components included lactic acid, bacteriocins and hydrogen peroxide. Overall, MLm SCB2557 was effective in inhibiting the growth of S. liquefaciens, which provided a theoretical basis for developing natural antimicrobial agents in the food industry.