Whether growing in a puddle of dirty water or inside the human body, large groups of bacteria must coordinate their behavior to perform essential tasks that they would not be able to carry out individually. Bacteria achieve this coordination through a process called quorum sensing in which the microorganisms produce and secrete small molecules called autoinducers that can be detected by neighboring bacterial cells. Only when a large number of bacteria are present can the levels of secreted autoinducer build up to the point where the community can detect them and respond as a coordinated group.