title: Single-cell, real-time detection of oxidative stress induced in Escherichia coli by the antimicrobial peptide CM15.
abstract: Antibiotics target specific biochemical mechanisms in bacteria. In response to new drugs, pathogenic bacteria rapidly develop resistance. In contrast, antimicrobial peptides (AMPs) have retained broad spectrum antibacterial potency over millions of years. We present single-cell fluorescence assays that detect reactive oxygen species (ROS) in the Escherichia coli cytoplasm in real time. Within 30 s of permeabilization of the cytoplasmic membrane by the cationic AMP CM15 [combining residues 1-7 of cecropin A (from moth) with residues 2-9 of melittin (bee venom)], three fluorescence signals report oxidative stress in the cytoplasm, apparently involving O2 (-), H2O2, and •OH. Mechanistic studies indicate that active respiration is a prerequisite to the CM15-induced oxidative damage. In anaerobic conditions, signals from ROS are greatly diminished and the minimum inhibitory concentration increases 20-fold. Evidently the natural human AMP LL-37 also induces a burst of ROS. Oxidative stress may prove a significant bacteriostatic mechanism for a variety of cationic AMPs. If so, host organisms may use the local oxygen level to modulate AMP potency.
authors.affiliation: Department of Chemistry and.
authors.forename: Heejun
authors.identifier: http://orcid.org/0000-0003-2136-9598
authors.initials: H
authors.lastname: Choi
authors.affiliation: Department of Chemistry and.
authors.forename: Zhilin
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Department of Chemistry and Molecular Biophysics Program, University of Wisconsin, Madison, WI 53706 weisshaar@chem.wisc.edu.
authors.forename: James C
authors.initials: JC
authors.lastname: Weisshaar
mesh_terms: D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects* / Q000378:metabolism; D005453:Fluorescence; D008826:Microbial Sensitivity Tests; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D023181:Antimicrobial Cationic Peptides; D017382:Reactive Oxygen Species; C513873:antimicrobial hybrid peptide CM15
keywords: CM15; E. coli; antimicrobial peptide; oxidative stress; real-time ROS assay