Related Experiment Video
Updated: May 8, 2026

Quantification of Violacein in Chromobacterium violaceum and Its Inhibition by Bioactive Compounds
Published on: August 8, 2025
Indole inhibits bacterial quorum sensing signal transmission by interfering with quorum sensing regulator folding
1Department of Environmental Science and Ecological Engineering, Korea University, Seoul 136-713, Republic of Korea.
Abstract:
Quorum sensing (QS)-dependent biofilm formation and motility were controlled by AqsR in Acinetobacter oleivorans DR1. QS-controlled phenotypes appeared to be inhibited by indole and the aqsR mutant had the same phenotypes. We demonstrated that the turnover rate of AqsR became more rapid without the N-acylhomoserine lactone (AHL) signal, and that indole could increase the expression of many protease and chaperone proteins. The addition of exogenous indole decreased the expression of two AqsR-targeted genes: AOLE_03905 (putative surface adhesion protein) and AOLE_11355 (L-asparaginase). The overexpression of AqsR in Escherichia coli was impossible with the indole treatment. Surprisingly, our [(35)S]methionine pulse-labelling data demonstrated that the stability and folding of AqsR protein decreased in the presence of indole without changing aqsR mRNA expression in E. coli. Interestingly, indole resulted in a loss of TraR-dependent traG expression in an Agrobacterium tumefaciens indicator strain. However, when indole was added after incubation with exogenous AHL, indole could not inhibit the TraR-dependent expression of the traG promoter. This indicated that AHL-bound TraR could be protective against indole, but TraR without AHL could not be active in the presence of indole. Here, we provided evidence for the first time showing that the indole effect on QS-controlled bacterial phenotypes is due to inhibited QS regulator folding and not a reduced QS signal.
Related Concept Videos
Gene Regulation in Microbial Communities: Quorum Sensing
Bacterial Signaling
Inhibitors of Bacterial DNA Synthesis
Eukaryotic Transcription Inhibitors
Eukaryotic transcription inhibitors usually contain two distinct domains, a DNA...
Inhibitors of Bacterial Protein Synthesis
Inducible Operons: lac Operon

