Summary: A restriction endonuclease map was derived for the aromatic amine and -toluate catabolic plasmid pTDN1 present in UCC22, a derivative of mt-2. The plasmid is 79 ± 1 kbp in size and can be divided into a restriction-site-deficient region of 51 ± 1 kbp and a restriction-site-profuse region of 28 kbp which begins and ends with directly repeating sequences of at least 2 kbp in length. A mutant plasmid isolated after growth of the host on benzoate had lost the restriction-profuse region by a straightforward recombinational loss retaining one copy of the direct repeat. Analysis of clones, deletion and Tn insertion mutants strongly suggested that the -cleavage pathway of pTDN1 was situated in the region readily deleted. The catechol 2,3-dioxygenase (C23O) gene of pTDN1 showed no hybridization or restriction homology to previously described C230 genes of TOL plasmids pWW0 and pWW15. In addition, there was little homology between intact pTDN1, pWW0 and pWW15, suggesting the presence of a unique -cleavage pathway. We also demonstrated that pTDN1 did not originate from mt-2 chromosome.


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