The term "autoinduction" was first coined in 1970, when it was observed that the bioluminescent marine bacterium Vibrio fischeri produced a luminescent enzyme (luciferase) only when cultures had reached a threshold population density.  At low cell concentrations, V. fischeri did not express the luciferase gene. However, once the cultures had reached exponential growth phase, the luciferase gene was rapidly activated.  This phenomenon was termed “autoinduction” because it involved a molecule (autoinducer) that accumulated in a growth medium and induced the synthesis of components of the luminescence system.  Subsequent research revealed that the actual autoinducer used by V. fischeri is an acylated homoserine lactone (AHL) signaling molecule.