FIG. 7.

The divergent promoter region between phzR and the phz operon of P. fluorescens 2-79 contains cis-acting sites required for PhzR-mediated activation. The nucleotide sequence of the 379-bp region between phzR and phzA (A) contains putative −10 and −35 elements and ribosomal binding sites (RBS) as marked. The transcriptional start sites, shown as arrows labeled +1, were determined by primer extension analysis for phzA (B) and phzR (C) as described in Materials and Methods. The region also contains an 18-bp almost perfect inverted-repeat (phz box) that is related to the lux box sequence of Vibrio fischeri and also to inverted repeats located in the promoter regions of the phz operons of P. aureofaciens 30-84 and P. chlororaphis PCL1391 (D).