Indole: a signaling molecule or a mere metabolic byproduct that alters bacterial physiology at a high concentration?

Jisun Kim, Woojun Park

Research output: Contribution to journalReview articlepeer-review

106 Citations (Scopus)


Indole is an organic compound that is widespread in microbial communities inhabiting diverse habitats, like the soil environment and human intestines. Measurement of indole production is a traditional method for the identification of microbial species. Escherichia coli can produce millimolar concentrations of indole in the stationary growth phase under nutrient-rich conditions. Indole has received considerable attention because of its remarkable effects on various biological functions of the microbial communities, for example, biofilm formation, motility, virulence, plasmid stability, and antibiotic resistance. Indole may function as an intercellular signaling molecule, like a quorum-sensing signal. Nevertheless, a receptor system for indole and the function of this compound in coordinated behavior of a microbial population (which are requirements for a true signaling molecule) have not yet been confirmed. Recent findings suggest that a long-known quorum-sensing regulator, E. coli’s SdiA, cannot recognize indole and that this compound may simply cause membrane disruption and energy reduction, which can lead to various changes in bacterial physiology including unstable folding of a quorum-sensing regulator. Indole appears to be responsible for acquisition of antibiotic resistance via the formation of persister cells and activation of an exporter. This review highlights and summarizes the current knowledge about indole as a multitrophic molecule among bacteria, together with recently identified new avenues of research.

Original languageEnglish
Pages (from-to)421-428
Number of pages8
JournalJournal of Microbiology
Issue number7
Publication statusPublished - 2015 Jul 29

Bibliographical note

Publisher Copyright:
© 2015, The Microbiological Society of Korea and Springer-Verlag Berlin Heidelberg.


  • SdiA
  • antibiotic resistance
  • indole
  • protein folding
  • quorum sensing
  • signaling

ASJC Scopus subject areas

  • Microbiology
  • Applied Microbiology and Biotechnology


Dive into the research topics of 'Indole: a signaling molecule or a mere metabolic byproduct that alters bacterial physiology at a high concentration?'. Together they form a unique fingerprint.

Cite this