Weissellicin LM85 Purified from Weissella confusa LM85 Effluxes Potassium Ions and Depletes Proton Motive Force in Escherichia coli ATCC 25922

Bacteriocins are membrane-acting peptides and generally kill closely related bacteria using pore formation. In this study, we have studied a bacteriocin, weissellicin LM85 from Weissella confusa LM85 to monitor its antimicrobial activity against Escherichia coli ATCC 25922. It was purified from cell-free supernatant of W. confusa LM85 with molecular weight ~ 6.5 kDa and showed minimum inhibitory concentration, 138.3 µg/mL and minimum bactericidal concentration, 553.3 µg/mL against E. coli ATCC 25922. The loss of cell-viability, tested by staining with propidium iodide, suggested bactericidal effect of weissellicin LM85. There was efflux of potassium (K⁺) ions, dissipation of membrane potential (∆ψ) and transmembrane pH gradient (∆pH) in bacteriocin-treated cells. The target cells were found swollen and ruptured when visualized under electron microscope. It inhibited range of Gram-positive and Gram-negative bacteria such as Lactiplantibacillus plantarum NRRL B-4496, Lpb. plantarum LD4, Lactobacillus acidophilus NRRL B-4495, Enterococcus faecium NRRL B-2354, E. hirae LD3, E. faecalis ATCC 29212, Pediococcus pentosaceus LB44, Vibrio sp., Salmonella enterica subsp. enterica serovar Typhimurium ATCC 13311, Shigella flexneri, Staphylococcus aureus ATCC 25923 and Pseudomonas aeruginosa ATCC 27853. The above results indicate weissellicin LM85 is a membrane-acting peptide with broad host-range of antimicrobial activity and may be used as alternative to clinical antibiotics.