Indole Signaling in Microbial Communities
Summary
Indole, a heterocyclic aromatic compound derived from tryptophan catabolism, has emerged as a central signalling molecule in both Gram-negative and Gram-positive bacteria. Synthesised predominantly by the enzyme tryptophanase, indole accumulates in stationary-phase cultures and diffuses across cell membranes, where it modulates gene expression and cellular physiology. In individual species, indole regulates motility, biofilm formation and virulence factor production, often acting through specific receptors such as the transcription factor SdiA or via two-component regulatory systems. In mixed populations, indole serves as an inter-species cue, coordinating community architecture, antibiotic tolerance and metabolic interactions. Derivatives of indole, including halogenated analogues, expand this chemical lexicon, offering tunable effects on persister cell eradication and quorum-sensing interference. Beyond basic biology, indole signalling has inspired antivirulence strategies, microbiome engineering and novel approaches to biofilm control in medical and industrial settings.
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Indole Signaling in Microbial Communities publication trend
The graph below shows the total number of articles in indole signaling in microbial communities across all publications each year (not limited to Nature Index journals).
Technical terms
Indole: An aromatic signalling molecule produced by bacterial tryptophanase that regulates community behaviour and physiology.
Quorum sensing: Population-density-dependent communication in bacteria mediated by diffusible signals to coordinate collective processes.
Biofilm: A structured multicellular consortium embedded in an extracellular polymeric matrix that confers enhanced tolerance to stresses.
Persister cell: A dormant, non-dividing bacterial subpopulation highly tolerant to antibiotics and implicated in chronic infections.
Two-component system: A common bacterial signal transduction mechanism comprising a sensor kinase and a response regulator that modulates gene expression in response to stimuli.
References
- Indole is an inter-species biofilm signal mediated by SdiA. BMC Microbiology (2007).
- The Indole Pulse: A New Perspective on Indole Signalling in Escherichia coli. PLOS ONE (2014).
- Indole signaling in Escherichia coli: a target for antivirulence therapy?. Gut Microbes (2025).
- Halogenated indoles eradicate bacterial persister cells and biofilms. AMB Express (2016).
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