Plasmid gene organization: naphthalene/salicylate oxidation

Genes for naphthalene metabolism are localized on nah7, an 83-kilobase (kb) plasmid, in two gene clusters under salicylate control. Polar mutations formed by insertion of the transposon Tn5 permit detection of the transcription direction and the gene organization within two approximately 10-kb DNA segments separated by a approximately 7-kb regulatory gene region. The gene cluster specifying conversion of naphthalene to salicylate lies near the left initiation of a 25-kb DNA fragment A released by EcoRI; that for the salicylate pathway via catechol meta-fission lies near the right terminus with extension into the adjoining 5.9-kb fragment C. The genetic organization and regulation resemble the tol plasmid-encoded "upper" and "lower" pathways of toluene/xylene oxidation in Pseudomonas putida mt2.