PotF Affects the Antibacterial Activity of Plantaricin BM-1 Against Escherichia coli K12 by Modulating Biofilm Formation and Cell Membrane Integrity.

Plantaricin BM-1 exhibits antibacterial activity against Escherichia coli; however, the underlying mechanism remains unclear. This study aimed to investigate the function of PotF, a putrescine-binding protein, in regulating the antibacterial activity of plantaricin BM-1 against E. coli K12. The antibacterial activity of plantaricin BM-1 against E. coli K12 and JW0838 cells was assessed using growth curves. The differences in biofilm formation between the two E. coli strains were evaluated by crystal violet staining and confocal laser scanning microscopy. The effects of plantaricin BM-1 on E. coli morphology and cell membrane integrity were investigated by electron microscopy and lactate dehydrogenase release assays. Proteomics was used to screen for differentially expressed proteins (DEPs) that are potentially involved in regulating the antibacterial mechanism. The null mutation of potF enhanced the antibacterial effects of plantaricin BM-1 on E. coli, and caused a significant decrease (p < 0.05) in the biofilms of E. coli JW0838. The plantaricin disrupted the cell membrane of E. coli JW0838. Proteomic analysis revealed that potF mutation significantly affected several DEPs involved in biofilm formation. Plantaricin BM-1 exhibited significantly enhanced antibacterial activity against biofilm-associated gene mutants compared to wild-type E. coli K12. These findings enhance our understanding of the bacteriostasis of class IIa bacteriocins against Gram-negative microorganisms.