Roles of indole as an interspecies and interkingdom signaling molecule.

A number of bacteria, and some plants, produce large quantities of indole, which is widespread in animal intestinal tracts and in the rhizosphere. Indole, as an interspecies and interkingdom signaling molecule, plays important roles in bacterial pathogenesis and eukaryotic immunity. Furthermore, indole and its derivatives are viewed as potential antivirulence compounds against antibiotic-resistant pathogens because of their ability to inhibit quorum sensing and virulence factor production. Indole modulates oxidative stress, intestinal inflammation, and hormone secretion in animals, and it controls plant defense systems and growth. Insects and nematodes can recognize indole, which controls some of their behavior. This review presents current knowledge regarding indole and its derivatives, their biotechnological applications and their role in prokaryotic and eukaryotic systems.