Antimicrobial peptides against Pseudomonas syringae pv. actinidiae and Erwinia amylovora: Chemical synthesis, secondary structure, efficacy, and mechanistic investigations. Issue 1 (January 2014)

• Record Type: Journal Article
• Authors: Cameron, Alan; Zoysa, Gayan Heruka De; Sarojini, Vijayalekshmi
• Is Part Of: Biopolymers. Volume 102:Issue 1(2014)
• Page Start: 88
• Page End: 96
• Publication Date: 2014-01
• Subjects: Biopolymers -- Periodicals; Peptides -- Periodicals; Spectrum analysis -- Periodicals; 572.33
• DOI: 10.1002/bip.22423
• Languages: English
• ISSNs: 0006-3525

Abstract

<abstract abstract-type="main"> <title>ABSTRACT</title> <p>We report on structurally modified dodecapeptide amides (KYKLFKKILKFL‐NH<sub>2</sub>) and two analogs of a hexapeptide amide (WRWYCR‐NH<sub>2</sub>) with antibacterial activity against the Gram negative pathogens <italic>Pseudomonas syringae</italic> pv. <italic>actinidiae</italic> (Psa) and <italic>Erwinia amylovora</italic> (Ea). Dodecapeptide minimal inhibitory concentrations (MICs) ranged from 3.2 to 15.4 µ<italic>M</italic>, with the unmodified peptide being the most potent against both pathogens. The unmodified dodecapeptide also had 32–58% α‐helicity in membrane mimetic environments (50% v/v trifluoroethanol and 30 m<italic>M</italic> SDS micelles). Structural modifications which included branching, acylation, and conjugation with 5‐nitro‐2‐furaldehyde (NFA) proved detrimental to both antimicrobial activity and α‐helicity. Scanning electron microscopy (SEM) revealed distinct morphological changes to bacterial cells treated with the different peptides, leading to blistering of the membrane and cell lysis. MICs of the hexapeptide amide were 3.9–7.7 µ<italic>M</italic> against both pathogens. The hexapeptide acid did not show anti‐bacterial activity against either pathogen. However, the NFA conjugated hexapeptide acid was more active than the parent peptide or NFA alone with MICs of 1.6–3.2 µ<italic>M</italic> against the pathogens. SEM analysis revealed shriveling and collapse of bacterial cells treated with the hexapeptide, whereas shortening and compactness on exposure to streptomycin. A colorimetric assay demonstrated that the dodecapeptides were likely to act by targeting the bacterial membrane, whereas the hexapeptides, streptomycin, and NFA were not, thereby supporting the morphological changes observed during SEM. To the best of our knowledge, this appears to be the first report of antimicrobial peptide activity against Psa, a pathogen that is currently devastating the kiwifruit industry internationally. © 2013 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 102: 88–96, 2014.</p> </abstract>