Transcriptome Analysis of the Vibrio fischeri LuxR-LuxI Regulon

expression of the seven-gene luminescence operon. We used microarrays to unveil 18 additional 3OC6-HSL-controlled genes, 3 of which had been identified by other means previously. We show most of these genes are regulated by the 3OC6-HSL-responsive transcriptional regulator LuxR directly. This demonstrates that V. fischeri quorum sensing regulates a substantial number of genes other than those involved in light production. Quorum sensing allows a species to measure its population density and control gene expression in a population density-dependent manner. Bacterial quorum sensing involves cell-cell communication mediated by extracellular signal compounds. Various species of proteobacteria use acyl-homoserine lac-tones (acyl-HSLs) as quorum-sensing signals (2, 12–15, 36, 42). Acyl-HSL quorum sensing was first described in the marine luminescent bacterium Vibrio fischeri, where it controls tran-scription of the luminescence (lux) operon (7, 10, 11). The LuxI acyl-HSL synthase and the LuxR transcriptional activator constitute the quorum-sensing system, which controls the lu