N-Acetylglucosamine Inhibits LuxR, LasR and CviR Based Quorum Sensing Regulated Gene Expression Levels

Area of Science:

• Microbiology
• Biochemistry
• Molecular Biology

Background:

• Chitin, a natural polymer, is broken down into N-acetyl-D-glucosamine (NAG).
• Bacteria use N-acyl-L-homoserine lactone (AHL) mediated quorum sensing (QS) to regulate chitinase production for NAG generation.

Purpose of the Study:

• To investigate the impact of NAG on QS-regulated gene expression mediated by LuxR, LasR, and CviR.
• To determine if NAG affects reporter gene (GFP), violacein, and extracellular chitinase expression.

Main Methods:

• Utilized AHL reporter strains to examine NAG's effect on QS-regulated gene expression.
• Measured inhibition of AHL-dependent gene transcription, violacein production, and extracellular enzyme activity.

Main Results:

• NAG significantly inhibited AHL-dependent gene transcription (50-80% reduction) at low millimolar concentrations.
• Evidence suggests NAG acts via competitive inhibition at the AHL binding site and catabolite repression.
• NAG modulated CviR-regulated phenotypes, down-regulating violacein and up-regulating extracellular enzymes.

Conclusions:

• NAG exhibits quorum sensing inhibiting activity, acting through competitive inhibition and catabolite repression.
• An unknown regulatory component influenced by NAG affects CviR-dependent phenotype expression.
• NAG represents a novel compound with QS inhibiting properties, contributing to a growing list of such molecules.