title: The Mechanism of Killing by the Proline-Rich Peptide Bac7(1-35) against Clinical Strains of Pseudomonas aeruginosa Differs from That against Other Gram-Negative Bacteria.
abstract: Pseudomonas aeruginosainfections represent a serious threat to worldwide health. Proline-rich antimicrobial peptides (PR-AMPs), a particular group of peptide antibiotics, have demonstratedin vitroactivity againstP. aeruginosastrains. Here we show that the mammalian PR-AMP Bac7(1-35) is active against some multidrug-resistant cystic fibrosis isolates ofP. aeruginosaBy confocal microscopy and cytometric analyses, we investigated the mechanism of killing againstP. aeruginosastrain PAO1 and three selected isolates, and we observed that the peptide inactivated the target cells by disrupting their cellular membranes. This effect is deeply different from that previously described for PR-AMPs inEscherichia coliandSalmonella entericaserovar Typhimurium, where these peptides act intracellularly after having been internalized by means of the transporter SbmA without membranolytic effects. The heterologous expression of SbmA in PAO1 cells enhanced the internalization of Bac7(1-35) into the cytoplasm, making the bacteria more susceptible to the peptide but at the same time more resistant to the membrane lysis, similarly to what occurs inE. coliThe results evidenced a new mechanism of action for PR-AMPs and indicate that Bac7 has multiple and variable modes of action that depend on the characteristics of the different target species and the possibility to be internalized by bacterial transporters. This feature broadens the spectrum of activity of the peptide and makes the development of peptide-resistant bacteria a more difficult process.
authors.affiliation: Department of Life Sciences, University of Trieste, Trieste, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Runti
authors.affiliation: Department of Life Sciences, University of Trieste, Trieste, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Benincasa
authors.affiliation: Department of Life Sciences, University of Trieste, Trieste, Italy.
authors.forename: Grazia
authors.initials: G
authors.lastname: Giuffrida
authors.affiliation: Group of Bacteriology and Plant Bacteriology, International Centre for Genetic Engineering and Biotechnology, Trieste, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Devescovi
authors.affiliation: Group of Bacteriology and Plant Bacteriology, International Centre for Genetic Engineering and Biotechnology, Trieste, Italy.
authors.forename: Vittorio
authors.initials: V
authors.lastname: Venturi
authors.affiliation: Department of Life Sciences, University of Trieste, Trieste, Italy.
authors.forename: Renato
authors.initials: R
authors.lastname: Gennaro
authors.affiliation: Department of Life Sciences, University of Trieste, Trieste, Italy mscocchi@units.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Scocchi
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000138:chemical synthesis / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000138:chemical synthesis / Q000494:pharmacology*; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects* / Q000648:ultrastructure; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D018613:Microscopy, Confocal; D021381:Protein Transport; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D012486:Salmonella typhimurium / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity; D019076:Transgenes
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; C481640:Bac7(1-35) peptide; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; C529573:SbmA protein, E coli
keywords: Bac7; Pseudomonas aeruginosa; antimicrobial peptide; cystic fibrosis isolate; mechanism of action; proline rich