Editing Quorum sensing (section)

====''Aliivibrio fischeri''====
The bioluminescent bacterium ''[[Aliivibrio fischeri]]'' is the first organism in which QS was observed. It lives as a [[mutualism (biology)|mutualistic]] [[symbiont]] in the [[photophore]] (or light-producing organ) of the [[Hawaiian bobtail squid]]. When ''A. fischeri'' cells are free-living (or [[plankton]]ic), the autoinducer is at low concentration, and, thus, cells do not show luminescence. However, when the population reaches the threshold in the photophore (about {{10^|11}} cells/ml), transcription of [[luciferase]] is induced, leading to [[bioluminescence]].
In ''A. fischeri'', bioluminescence is regulated by AHLs (N-acyl-homoserine lactones) which is a product of the LuxI gene whose transcription is regulated by the LuxR activator. LuxR works only when AHLs binds to the LuxR.