Medium effects on minimum inhibitory concentrations of nylon-3 polymers against E. coli

Minimum inhibitory concentrations (MICs) against E. coli were measured for three nylon-3 polymers using Luria-Bertani broth (LB), brain-heart infusion broth (BHI), and a chemically defined complete medium (EZRDM). The polymers differ in the ratio of hydrophobic to cationic subunits. The cationic hom...

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Bibliographic Details
Published in:PloS one 2014-08, Vol.9 (8), p.e104500
Main Authors: Choi, Heejun, Chakraborty, Saswata, Liu, Runhui, Gellman, Samuel H, Weisshaar, James C
Format: Article
Language:English
Subjects:
Amino acids
Anti-Bacterial Agents - chemistry
Anti-Bacterial Agents - pharmacology
Antiinfectives and antibacterials
Antimicrobial Cationic Peptides - chemistry
Antimicrobial peptides
Bacteria
Biology and Life Sciences
Biophysics
Brain
Casein
Cationic polymerization
Chemistry
Design
Drug resistance
E coli
Escherichia coli
Escherichia coli - drug effects
Hydrophobic and Hydrophilic Interactions
Hydrophobicity
Lipopolysaccharides
Membranes
Microbial Sensitivity Tests
N-Terminus
Nylon
Nylons - chemistry
Nylons - pharmacology
Pathogens
Peptides
Polymers
Polymers - chemistry
Polymers - pharmacology
Salmonella
Structure-Activity Relationship
Studies
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Summary:Minimum inhibitory concentrations (MICs) against E. coli were measured for three nylon-3 polymers using Luria-Bertani broth (LB), brain-heart infusion broth (BHI), and a chemically defined complete medium (EZRDM). The polymers differ in the ratio of hydrophobic to cationic subunits. The cationic homopolymer is inert against E. coli in BHI and LB, but becomes highly potent in EZRDM. A mixed hydrophobic/cationic polymer with a hydrophobic t-butylbenzoyl group at its N-terminus is effective in BHI, but becomes more effective in EZRDM. Supplementation of EZRDM with the tryptic digest of casein (often found in LB) recapitulates the LB and BHI behavior. Additional evidence suggests that polyanionic peptides present in LB and BHI may form electrostatic complexes with cationic polymers, decreasing activity by diminishing binding to the anionic lipopolysaccharide layer of E. coli. In contrast, two natural antimicrobial peptides show no medium effects. Thus, the use of a chemically defined medium helps to reveal factors that influence antimicrobial potency of cationic polymers and functional differences between these polymers and evolved antimicrobial peptides.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0104500