THE LUXR REGULATOR PROTEIN CONTROLS SYNTHESIS OF POLYHYDROXYBUTYRATE IN VIBRIO-HARVEYI

The LuxR regulatory protein of Vibrio harveyi has been shown to contro l synthesis of polyhydroxybutyrate (PHB) as well as luminescence so as to occur at high cell density, suggesting that it is a general regula tory protein, Mutants defective in the production of LuxR (D1, D34, an d MR1130) were found to be missing PHB, whose synthesis could be resto red by complementation with luxR. Triparental mating with a V. harveyi genomic library revealed the presence of three genomic clones (G1, G2 and G3) that could also restore PHB synthesis and luminescence to cel ls which express low levels of luxR (D1 and D34) but not to luxR(-) ce lls (MR1130) suggesting that luxR expression was being stimulated. Ana lyses of luxR mRNA levels by mRNA dot blot hybridization and by primer extension confirmed that luxR mRNA levels were increased 4 to 7-fold in the D1 and D34 cells by the G1, G2 and G3 fragments and show that e xpression of a single genomic copy of luxR is sufficient to restore sy nthesis of PHB. The results demonstrate that V. harveyi LuxR controls the induction of a process not intimately involved in the bioluminesce nce system and clearly distinguishes its role in V. harveyi from that of LuxR from Vibrio (Photobacterium) fischeri, which has only been ass ociated with regulation of light emission. (C) 1998 Elsevier Science B .V. All rights reserved.