Disruption and Proteome Alterations of Escherichia coli Induced by a Novel Antimicrobial Peptide from Tibetan Kefir

Abstract

Our previous study has demonstrated the broad spectrum of antibacterial activities of a novel peptide F1 against fungi, gram‐positive and gram‐negative bacteria. F1 was produced by Lactobacillus paracasei subsp. Tolerans FX‐6 isolated from Tibetan kefir. This study was aimed to reveal the mechanisms for the antibacterial effects of F1 on Escherichia coli using transmission electron microscope and iTRAQ‐based quantitative proteomic analysis. The ultrastructural observation showed that the Escherichia coli cells shrunk after being treated with F1 for 0.5 h or 1 h, suggesting that there was a large extent of cytoplasmic leak. After 2 h, the cell was completely deformed and lysed. The results from iTRAQ‐based quantitative proteomic analysis showed that among 280 identified proteins in Escherichia coli, there were 31 proteins with significantly altered expression levels in response to the treatment of antimicrobial peptide F1, including 10 down‐regulated proteins and 21 up‐regulated proteins. Each of these proteins has different molecular functions according to the Kyoto Encyclopedia of Genes and Genomes pathways. Specifically, the tricarboxylic acid cycle, oxidative phosphorylation, glycerophospholipid metabolism, and cell cycle‐caulobacter pathways, which are associated with Escherichia coli cell death, were affected to the largest extent by the antimicrobial peptide F1. Overall, our study demonstrated a global response of Escherichia coli to the antimicrobial peptide F1, which provides novel insights on the mechanisms of antimicrobial peptides.