title: Interaction of the antimicrobial peptides caerin 1.1 and aurein 1.2 with intact bacteria by2H solid-state NMR.
abstract: Nuclear magnetic resonance (NMR) is commonly used to probe the effect of antimicrobial agents on bacterial membranes using model membrane systems. Ideally, considering the complexity of membranes, the interaction of molecules with membranes should be studied in vivo. The interactions of two antimicrobial peptides (AMPs) with intact Escherichia coli and Bacillus subtilis were investigated using deuterium solid-state NMR. Specifically, we studied caerin 1.1 and aurein 1.2 isolated from the skin of Australian tree frogs. The minimal inhibitory concentration value for E. coli and B. subtilis was about 100μg/mL and 30μg/mL, respectively, for both peptides. A protocol to deuterate the membrane phospholipids of non-mutated B. subtilis was established using deuterated palmitic acid.2H NMR spectra combined with spectral moment analysis support the interaction of the two AMPs with the hydrophobic core of the bacterial membranes. The presence of peptides decreased the order of the lipid acyl chains for both E. coli and B. subtilis, but at higher peptide concentrations for the Gram(+) bacteria. This may be explained by the presence of other cell wall components, such as the negatively-charged teichoic and lipoteichoic acids in the peptidoglycan, which would interact with the AMPs and decrease their actual concentration on the membrane surface. The mechanism of action of the AMPs thus depends on their local concentration as well as the membrane environment. The differences between the AMPs interaction with E. coli and B. subtilis reveal the importance of studying intact bacteria.
authors.affiliation: Department of Chemistry, Université du Québec à Montréal, P.O. Box 8888, Downtown Station, Montréal H3C 3P8, Canada.
authors.forename: Marwa
authors.initials: M
authors.lastname: Laadhari
authors.affiliation: Department of Chemistry, Université du Québec à Montréal, P.O. Box 8888, Downtown Station, Montréal H3C 3P8, Canada.
authors.forename: Alexandre A
authors.initials: AA
authors.lastname: Arnold
authors.affiliation: Department of Chemistry, Université du Québec à Montréal, P.O. Box 8888, Downtown Station, Montréal H3C 3P8, Canada.
authors.forename: Andrée E
authors.initials: AE
authors.lastname: Gravel
authors.affiliation: School of Chemistry, Bio21 Institute, University of Melbourne, VIC 3010, Australia.
authors.forename: Frances
authors.initials: F
authors.lastname: Separovic
authors.affiliation: Department of Chemistry, Université du Québec à Montréal, P.O. Box 8888, Downtown Station, Montréal H3C 3P8, Canada. Electronic address: marcotte.isabelle@uqam.ca.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Marcotte
mesh_terms: D029845:Amphibian Proteins / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D001412:Bacillus subtilis / Q000187:drug effects*; D002462:Cell Membrane / Q000187:drug effects; D003903:Deuterium; D004926:Escherichia coli / Q000187:drug effects*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008826:Microbial Sensitivity Tests
chemical_list: D029845:Amphibian Proteins; D023181:Antimicrobial Cationic Peptides; C506635:aurein 1.2 peptide; C107616:caerin 1.1, Anura; D003903:Deuterium
keywords: Action mechanism; Bacillus subtilis; Escherichia coli; Gram-positive and Gram-negative bacteria; In-cell NMR; Membrane interactions