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Antimicrobial Peptides Produced by Selective Pressure Incorporation of Non-canonical Amino Acids
Published on: May 4, 2018
pH Dependence of microbe sterilization by cationic antimicrobial peptides
William F Walkenhorst1, J Wolfgang Klein, Phuong Vo
1Loyola University New Orleans, Department of Chemistry, New Orleans, Louisiana, USA. walken@loyno.edu
Antimicrobial Agents and Chemotherapy
|May 8, 2013
Summary
Cationic antimicrobial peptides (CAMPs) show varying effectiveness based on pH and ionic strength. Their efficacy against Gram-negative bacteria and fungi decreases at high pH, but surprisingly increases for Staphylococcus aureus.
Area of Science:
- Biochemistry
- Microbiology
- Peptide Science
Background:
- Cationic antimicrobial peptides (CAMPs) are crucial in innate immunity and are being developed as therapeutics.
- Previous studies highlighted CAMPs' broad-spectrum activity under specific conditions (neutral pH, low ionic strength).
- Understanding environmental factors influencing CAMP efficacy is vital for their application.
Purpose of the Study:
- To investigate the impact of pH and ionic strength on the antimicrobial activity of a newly identified CAMP family.
- To determine how solution conditions affect CAMP efficacy against diverse microorganisms.
- To elucidate the mechanisms behind observed species-specific pH responses.
Main Methods:
- Selection of CAMPs from a combinatorial library.
- Determination of minimum sterilizing concentrations (MSCs) against a panel of microorganisms.
- Systematic variation of solution pH and ionic strength to assess peptide efficacy.
- Analysis of peptide charge and cell wall composition in relation to antimicrobial activity.
Main Results:
- CAMP minimum sterilizing concentrations (MSCs) demonstrated a linear correlation with pH across all tested organisms.
- CAMP efficacy against Gram-negative bacteria and Candida albicans diminished at higher pH.
- A contrasting pH trend was observed for Staphylococcus aureus, with increased efficacy at higher pH.
- Increasing ionic strength exacerbated the observed pH effects.
Conclusions:
- Solution conditions, particularly pH and ionic strength, significantly modulate CAMP activity.
- Species-specific pH responses are influenced by the cell wall composition, notably the peptidoglycan layer in Gram-positive bacteria.
- These findings have critical implications for the rational design and effective application of CAMP-based antimicrobials.
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