Regulation of naphthalene catabolic genes of plasmid NAH7

Tn5 insertion mutations defining a regulatory gene, nahR, of the naphthalene catabolic pathway encoded by the NAH7 plasmid were mapped within a small NAH7 region only a few hundred bases upstream of the nahG gene, the most promoter-proximal gene of the nahGHIJK operon. The nahR mutations blocked the induction of both the nahABCDEF and nahGHIJK operons, and the defect was completely corrected in the presence of the wild-type allele in a trans position. The pleiotropic, recessive, and negative nature of these mutations indicates that the nahR gene specifies a regulatory element which is required to activate both nah operons.