ArcA/ArcB and LuxR-LuxI-mediated regulation of bioluminescence in V. fischeri.

LuxI synthesizes 3OC6, a diffusible pheromone that upon reaching a sufficient concentration combines with LuxR. 3OC6-LuxR binds to the “lux box” and stimulates transcription of the luxICDABEG operon, which produces more 3OC6 and bioluminescence. The ArcA/ArcB two-component regulatory system responds to reducing conditions, and ArcA-P binds near the lux box, effectively inhibiting bioluminescence. Two other autoinducer pheromones AI-2 and C8-HSL are not shown, although the latter can also function with LuxR.