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A peptide derived from phage display library exhibits antibacterial activity against E. coli and Pseudomonas aeruginosa.

Sainath Rao S, Mohan KV, Atreya CD - PLoS ONE (2013)

Bottom Line: Emergence of drug resistant strains to currently available antibiotics has resulted in the quest for novel antimicrobial agents.The peptide was highly active against gram-negative organisms and showed significant bactericidal activity against E. coli and P. aeruginosa resulting in a reduction of 5 log(10) CFU/ml.Thus this study demonstrates that peptides identified to bind to bacterial cell surface through phage-display screening may additionally aid in identifying and developing novel antimicrobial peptides.

View Article: PubMed Central - PubMed

Affiliation: Section of Cell Biology, Laboratory of Cellular Hematology, Division of Hematology, Center for Biologics Evaluation and Research, US Food and Drug Administration, Bethesda, Maryland, United States of America.

ABSTRACT
Emergence of drug resistant strains to currently available antibiotics has resulted in the quest for novel antimicrobial agents. Antimicrobial peptides (AMPs) are receiving attention as alternatives to antibiotics. In this study, we used phage-display random peptide library to identify peptides binding to the cell surface of E. coli. The peptide with sequence RLLFRKIRRLKR (EC5) bound to the cell surface of E. coli and exhibited certain features common to AMPs and was rich in Arginine and Lysine residues. Antimicrobial activity of the peptide was tested in vitro by growth inhibition assays and the bacterial membrane permeabilization assay. The peptide was highly active against gram-negative organisms and showed significant bactericidal activity against E. coli and P. aeruginosa resulting in a reduction of 5 log(10) CFU/ml. In homologous plasma and platelets, incubation of EC5 with the bacteria resulted in significant reduction of E. coli and P. aeruginosa, compared to the peptide-free controls. The peptide was non-hemolytic and non-cytotoxic when tested on eukaryotic cells in culture. EC5 was able to permeabilize the outer membrane of E. coli and P. aeruginosa causing rapid depolarization of cytoplasmic membrane resulting in killing of the cells at 5 minutes of exposure. The secondary structure of the peptide showed a α-helical conformation in the presence of aqueous environment. The bacterial lipid interaction with the peptide was also investigated using Molecular Dynamic Simulations. Thus this study demonstrates that peptides identified to bind to bacterial cell surface through phage-display screening may additionally aid in identifying and developing novel antimicrobial peptides.

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Mechanism of action of EC5 against E. coli and P. aeruginosa.A. Outer-membrane permeabilization mediated by EC5 as assessed by NPN uptake. Effect of EC5 and Polymyxin B on NPN fluorescence. Value on y axis is the maximum fluorescence upon NPN uptake by the bacteria. B. EC5-induced permeability of bacterial cells studied using Syto9 and PI staining. Peptide treated cells had increased membrane permeability as seen by increase in red fluorescence whereas live or untreated cells showed increase in green fluorescence. C. Cytoplasmic membrane depolarization using the fluorescent dye diSC3-5. Corresponding values on y axis represents maximum intensity upon release of the dye mediated by EC5 plotted against time (min). D. EC5 mediated inhibition of ATP synthesis. ATP concentration was measured after the addition of EC5 and polymyxin B at various concentrations and the luminescence units measured.
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pone-0056081-g008: Mechanism of action of EC5 against E. coli and P. aeruginosa.A. Outer-membrane permeabilization mediated by EC5 as assessed by NPN uptake. Effect of EC5 and Polymyxin B on NPN fluorescence. Value on y axis is the maximum fluorescence upon NPN uptake by the bacteria. B. EC5-induced permeability of bacterial cells studied using Syto9 and PI staining. Peptide treated cells had increased membrane permeability as seen by increase in red fluorescence whereas live or untreated cells showed increase in green fluorescence. C. Cytoplasmic membrane depolarization using the fluorescent dye diSC3-5. Corresponding values on y axis represents maximum intensity upon release of the dye mediated by EC5 plotted against time (min). D. EC5 mediated inhibition of ATP synthesis. ATP concentration was measured after the addition of EC5 and polymyxin B at various concentrations and the luminescence units measured.

Mentions: Outer membrane permeabilizing activity of EC5 against E. coli and P. aeruginosa was determined using the fluorescent dye N-phenyl-1-napthylamine (NPN) assay. The outer membrane of a bacterial cell is impermeable to NPN under normal conditions. However permeabilization of outer membrane by antimicrobial peptides allows the uptake of NPN thereby leading to increase in fluorescence in the cell. Fig. 8A shows dose-dependent increase in fluorescence in the presence of NPN in E. coli and P. aeruginosa, indicating that the peptide EC5 was able to disrupt the outer membrane of E. coli and P. aeruginosa. The outer membrane permeabilizing activity of EC5 was compared to polymyxin B, a well-studied membrane permeabilizing agent [39]. When both E. coli and P. aeruginosa were incubated with EC5, an increase in fluorescence was observed that was higher than for polymyxin B at similar concentrations.


A peptide derived from phage display library exhibits antibacterial activity against E. coli and Pseudomonas aeruginosa.

Sainath Rao S, Mohan KV, Atreya CD - PLoS ONE (2013)

Mechanism of action of EC5 against E. coli and P. aeruginosa.A. Outer-membrane permeabilization mediated by EC5 as assessed by NPN uptake. Effect of EC5 and Polymyxin B on NPN fluorescence. Value on y axis is the maximum fluorescence upon NPN uptake by the bacteria. B. EC5-induced permeability of bacterial cells studied using Syto9 and PI staining. Peptide treated cells had increased membrane permeability as seen by increase in red fluorescence whereas live or untreated cells showed increase in green fluorescence. C. Cytoplasmic membrane depolarization using the fluorescent dye diSC3-5. Corresponding values on y axis represents maximum intensity upon release of the dye mediated by EC5 plotted against time (min). D. EC5 mediated inhibition of ATP synthesis. ATP concentration was measured after the addition of EC5 and polymyxin B at various concentrations and the luminescence units measured.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3569419&req=5

pone-0056081-g008: Mechanism of action of EC5 against E. coli and P. aeruginosa.A. Outer-membrane permeabilization mediated by EC5 as assessed by NPN uptake. Effect of EC5 and Polymyxin B on NPN fluorescence. Value on y axis is the maximum fluorescence upon NPN uptake by the bacteria. B. EC5-induced permeability of bacterial cells studied using Syto9 and PI staining. Peptide treated cells had increased membrane permeability as seen by increase in red fluorescence whereas live or untreated cells showed increase in green fluorescence. C. Cytoplasmic membrane depolarization using the fluorescent dye diSC3-5. Corresponding values on y axis represents maximum intensity upon release of the dye mediated by EC5 plotted against time (min). D. EC5 mediated inhibition of ATP synthesis. ATP concentration was measured after the addition of EC5 and polymyxin B at various concentrations and the luminescence units measured.
Mentions: Outer membrane permeabilizing activity of EC5 against E. coli and P. aeruginosa was determined using the fluorescent dye N-phenyl-1-napthylamine (NPN) assay. The outer membrane of a bacterial cell is impermeable to NPN under normal conditions. However permeabilization of outer membrane by antimicrobial peptides allows the uptake of NPN thereby leading to increase in fluorescence in the cell. Fig. 8A shows dose-dependent increase in fluorescence in the presence of NPN in E. coli and P. aeruginosa, indicating that the peptide EC5 was able to disrupt the outer membrane of E. coli and P. aeruginosa. The outer membrane permeabilizing activity of EC5 was compared to polymyxin B, a well-studied membrane permeabilizing agent [39]. When both E. coli and P. aeruginosa were incubated with EC5, an increase in fluorescence was observed that was higher than for polymyxin B at similar concentrations.

Bottom Line: Emergence of drug resistant strains to currently available antibiotics has resulted in the quest for novel antimicrobial agents.The peptide was highly active against gram-negative organisms and showed significant bactericidal activity against E. coli and P. aeruginosa resulting in a reduction of 5 log(10) CFU/ml.Thus this study demonstrates that peptides identified to bind to bacterial cell surface through phage-display screening may additionally aid in identifying and developing novel antimicrobial peptides.

View Article: PubMed Central - PubMed

Affiliation: Section of Cell Biology, Laboratory of Cellular Hematology, Division of Hematology, Center for Biologics Evaluation and Research, US Food and Drug Administration, Bethesda, Maryland, United States of America.

ABSTRACT
Emergence of drug resistant strains to currently available antibiotics has resulted in the quest for novel antimicrobial agents. Antimicrobial peptides (AMPs) are receiving attention as alternatives to antibiotics. In this study, we used phage-display random peptide library to identify peptides binding to the cell surface of E. coli. The peptide with sequence RLLFRKIRRLKR (EC5) bound to the cell surface of E. coli and exhibited certain features common to AMPs and was rich in Arginine and Lysine residues. Antimicrobial activity of the peptide was tested in vitro by growth inhibition assays and the bacterial membrane permeabilization assay. The peptide was highly active against gram-negative organisms and showed significant bactericidal activity against E. coli and P. aeruginosa resulting in a reduction of 5 log(10) CFU/ml. In homologous plasma and platelets, incubation of EC5 with the bacteria resulted in significant reduction of E. coli and P. aeruginosa, compared to the peptide-free controls. The peptide was non-hemolytic and non-cytotoxic when tested on eukaryotic cells in culture. EC5 was able to permeabilize the outer membrane of E. coli and P. aeruginosa causing rapid depolarization of cytoplasmic membrane resulting in killing of the cells at 5 minutes of exposure. The secondary structure of the peptide showed a α-helical conformation in the presence of aqueous environment. The bacterial lipid interaction with the peptide was also investigated using Molecular Dynamic Simulations. Thus this study demonstrates that peptides identified to bind to bacterial cell surface through phage-display screening may additionally aid in identifying and developing novel antimicrobial peptides.

Show MeSH
Related in: MedlinePlus