THE ROLE OF THE LUX AUTOINDUCER IN REGULATING LUMINESCENCE IN VIBRIO-HARVEYI - CONTROL OF LUXR EXPRESSION

Analysis of Vibrio harveyi dark autoinducer mutants has demonstrated t hat the level of LuxR was much lower than that observed in wild-type c ells. Complementation with luxR fully restored luminescence suggesting that the lux autoinducer may control expression of the luxR regulator y gene. By primer extension, the transcriptional start site of luxR wa s located 78 bp from the initiation codon. The level of the primer-ext ended product was enhanced upon addition of the lux autoinducer to the autoinducer mutants, which was confirmed by hybridization of lux mRNA with specific probes. By using chloramphenicol acetyltransferase as a reporter gene in a transcriptional fusion with luxR, the stimulatory effect of autoinducer on luxR expression was shown to occur at the lev el of the luxR promoter. The results provide evidence that the autoind ucer signal in V. harveyi can be transduced through luxR, resulting in stimulation of luminescence.