Membrane disruption and DNA binding of Staphylococcus aureus cell induced by a novel antimicrobial peptide produced by Lactobacillus paracasei subsp tolerans FX-6

Previously, we have isolated a novel bacteriocin, peptide Fl from Tibetan Kefir, and demonstrated its superior antimicrobial activity. However, its antimicrobial mechanism is still undefined. This study was aimed to elucidate the antimicrobial mechanism of peptide Fl against Staphylococcus aureus. The antimicrobial effects of peptide Fl were characterized by the following methods: chemical assay to quantify cytoplasmic fi-galactosidase leakage, atomic absorption spectrometry to measure the released potassium ions, transmission electron microscopy to visualize the cellular morphological changes, and electrophoresis analysis and atomic force microscopy together to exam the DNA binding activity. Our results revealed that peptide Fl exerted its bactericidal effects by damaging bacterial cell membranes and by binding to the genomic DNA in the cytoplasm, which both led to rapid cell death. (C) 2015 Elsevier Ltd. All rights reserved.