Requirement for autoinducer in transcriptional negative autoregulation of the Vibrio fischeri luxR gene in Escherichia coli.

The effect of a mutation in luxI (autoinducer synthetase gene) on transcription of luxR in the cloned Vibrio fischeri lux system (luxR, luxICDABE) was examined in Escherichia coli. For the luxI mutant, transcription from the luxR promoter (monitored with beta-galactosidase levels from a luxR::lacZ fusion, with LuxR supplied in trans) decreased fivefold, to levels of the luxI+ strain, only in the presence of added autoinducer. The results demonstrate that, as has been shown at the translational level, autoinducer is required for negative autoregulation of luxR at the transcriptional level.