Abstract: The aim of this study was to elucidate the mode of action of a novel bacteriocin Lac-B23 from Lactobacillus plantarum B23, a small peptide with broad-spectrum antimicrobial activity, on Pseudomonas fluorescens. P. fluorescens was susceptible to bacteriocin Lac-B23 action, leading to the release of intracellular ATP and inorganic phosphate. Bacteriocin Lac-B23 first destroyed the extracellular membrane and then dissipated both transmembrane potential (Δφ) and transmembrane pH gradient (DpH), leading to the formation of channels in the cell membrane. Clear changes in the morphological integrity of P. fluorescens were observed under scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The cell membrane was destroyed, leading to the death of cells. Bacteriocin Lac-B23 could affect the network structure of the biofilm produced by P. fluorescens and exhibited anti-biofilm activity.

Key words: lactic acid bacteria, bacteriocin, Pseudomonas fluorescens, biofilm, inhibition