Inhibitory effects of a novel antimicrobial peptide from kefir against Escherichia coli

Antimicrobial peptide F1, a novel antimicrobial peptide from Tibetan kefir, have shown strong antimicrobial activity against several bacteria and fungi. We identified the amino acid sequence and studied the antimicrobial mechanism of peptide F1 against Escherichia coli. Our results showed that antimicrobial peptide F1 contained 18 amino acids (Thr-DAP-Asn-Thr-PEA-His-Pro-Asn-Thr-His-Leu-Ile- PEA-CySHVal-Asn-PEA-Tau), which increased the outer and inner membrane permeability of E. coli, and the leakage of the cytoplasmic beta-galactosidase and potassium ions was detected in the process. Morphologies of E. coli were observed by confocal laser scanning microscopy and transmission electron microscopy, which visually showed that antimicrobial peptide F1 could penetrate and accumulate into cell causing disruption of cell membrane functions. Furthermore, we elucidated the DNA findings in that antimicrobial peptide F1 has multiple targets in the killing of E. coli. (C) 2016 Elsevier Ltd. All rights reserved.