Indole-3-acetic acid improves Escherichia coli's defences to stress

Arch Microbiol. 2006 Jun;185(5):373-82. doi: 10.1007/s00203-006-0103-y. Epub 2006 Mar 23.


Indole-3-acetic acid (IAA) is a ubiquitous molecule playing regulatory roles in many living organisms. To elucidate the physiological changes induced by IAA treatment, we used Escherichia coli K-12 as a model system. By microarray analysis we found that 16 genes showed an altered expression level in IAA-treated cells. One-third of these genes encode cell envelope components, or proteins involved in bacterial adaptation to unfavourable environmental conditions. We thus investigated the effect of IAA treatment on some of the structural components of the envelope that may be involved in cellular response to stresses. This showed that IAA-treated cells had increased the production of trehalose, lipopolysaccharide (LPS), exopolysaccharide (EPS) and biofilm. We demonstrated further that IAA triggers an increased tolerance to several stress conditions (heat and cold shock, UV-irradiation, osmotic and acid shock and oxidative stress) and different toxic compounds (antibiotics, detergents and dyes) and this correlates with higher levels of the heat shock protein DnaK. We suggest that IAA triggers an increased level of alert and protection against external adverse conditions by coordinately enhancing different cellular defence systems.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Physiological / genetics
  • Anti-Bacterial Agents / pharmacology
  • Biofilms / growth & development
  • Cold Temperature
  • Drug Resistance, Bacterial
  • Escherichia coli K12 / drug effects
  • Escherichia coli K12 / genetics
  • Escherichia coli K12 / physiology*
  • Escherichia coli K12 / radiation effects
  • Escherichia coli Proteins / metabolism
  • Gene Expression Profiling
  • HSP70 Heat-Shock Proteins / metabolism
  • Hot Temperature
  • Hydrogen-Ion Concentration
  • Indoleacetic Acids / pharmacology*
  • Lipopolysaccharides / biosynthesis
  • Microbial Viability
  • Oligonucleotide Array Sequence Analysis
  • Osmotic Pressure
  • Polysaccharides, Bacterial / biosynthesis
  • Trehalose / biosynthesis


  • Anti-Bacterial Agents
  • Escherichia coli Proteins
  • HSP70 Heat-Shock Proteins
  • Indoleacetic Acids
  • Lipopolysaccharides
  • Polysaccharides, Bacterial
  • indoleacetic acid
  • Trehalose
  • dnaK protein, E coli