Interference with AI-2-mediated bacterial cell–cell communication

In a process called quorum sensing, bacteria communicate with each other using chemical signal molecules. This allows bacterial populations to synchronize their behaviour, and to act in some respects as multicellular organisms. One chemical communication molecule, called autoinducer-2 (AI-2), is a universal molecule that bacteria use to communicate between species. Some species of bacteria are now shown to interfere with AI-2-directed communication. This may give them an advantage in mixed-species communities, in the human gut microflora for instance. Bacteria communicate by means of chemical signal molecules called autoinducers. This process, called quorum sensing, allows bacteria to count the members in the community and to alter gene expression synchronously across the population. Quorum-sensing-controlled processes are often crucial for successful bacterial–host relationships—both symbiotic and pathogenic. Most quorum-sensing autoinducers promote intraspecies communication, but one autoinducer, called AI-2, is produced and detected by a wide variety of bacteria and is proposed to allow interspecies communication1,2. Here we show that some species of bacteria can manipulate AI-2 signalling and interfere with other species' ability to assess and respond correctly to changes in cell population density. AI-2 signalling, and the interference with it, could have important ramifications for eukaryotes in the maintenance of normal microflora and in protection from pathogenic bacteria.