A 9.9-kilobase (kb) BAMIII restriction endonuclease fragment encoding the catA and catBC gene clusters was selected from a gene bank of the Pseudomonas aeruginosa PAO1c chromosome. The catA, catB, and catC genes encode enzymes that catalyze consecutive reactions in the catechol branch of the beta-ketoadipate pathway. A recombinant plasmid, pRo1783, which contains the 9.9-kb BAMIII restriction fragment complemented P. aeruginosa, mutants with lesions in the catA, catB, or catC gene; however, this fragment of chromosomal DNA did not contain any other catabolic gene which had been placed near the catA or catBC cluster based on cotransducibility of the loci. Restriction mapping, deletion subcloning, and complementation analysis showed that the order of the genes on the cloned chromosomal DNA fragment is catA, catB, catC. (Copyright (c) 1988, American Society for Microbiology.)