Characteristics of Synthesized Antibacterial Peptide W3-2 from Lactiplantibacillus plantarum and Its Inhibitory Effect on Staphylococcus aureus

A synthesized antimicrobial peptide (W3-2) from Lactiplantibacillus plantarum was found to have temperature, pH, proteases (papain, proteinase K, pepsin, trypsin, cellulase, and pectinase), and several chemical reagents (thylenediaminetetraacetic acid, urea, Tween, methanol, and ethanol). Its inhibitory effect against Staphylococcus aureus was investigated by determining the minimum inhibitory concentration (MIC) and bactericidal kinetics. The underlying mechanism was explored through measurement of extracellular K⁺ and ATP levels and nucleic acid and protein leakage, flow cytometry analysis, and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. The results showed that W3-2 had strong inhibitory effects on both Gram-positive and Gram-negative bacteria. It inhibited the growth of S. aureus with an MIC of 0.425 mg/mL. W3-2 increased the permeability of the bacterial cell membrane, leading to K⁺ efflux and thereby disrupting the integrity of the cell membrane. This resulted in the leakage of intracellular macromolecular substances (nucleic acids, proteins, and ATP) and damage to both intracellular and extracellular structures, ultimately causing bacterial cell death. This study provides a scientific basis for the development and utilization of W3-2 as a novel antimicrobial agent.