TRANSPOSITION OF THE TOL CATABOLIC GENES (TN4651) INTO THE DEGRADATIVE PLASMID PSAH OF ALCALIGENES SP O-1 ENSURES SIMULTANEOUS MINERALIZATION OF SULFO-SUBSTITUTED AND METHYL-SUBSTITUTED AROMATICS

Mixtures of 2-aminobenzenesulphonate (trivial name orthanilic acid, OA ) and 3-methylbenzoic acid (3-MB), which are degraded by enzymes of pl asmid-encoded pathways, can exert inhibition of growth and respiration in Alcaligenes sp. O-1 and Pseudomonas putida mt-2 depending on the r atio of their concentrations. The pronounced inhibition of Alcaligenes sp. O-1 growing on OA by the addition of equimolar amounts of 3-MB is characterized by a rapid inactivation of the OA-converting desulphona tion activity. The exconjugant Alcaligenes sp. O/T was selected for si multaneous breakdown of OA and 3-MB by assembling the catabolic pathwa ys from the plasmids pSAH (OA) and pWW0 (3-MB) of the above strains. T he transpositional insertion of the TOL catabolic genes (Tn4651) from pWW0 into the recombinant plasmid of the exconjugant O/T was detected by Southern blot hybridization using the TOL plasmid as a probe. The e xconjugant showed a rapid inactivation of OA desulphonation activity s imilar to the parent strain. However, following induction of the TOL c atabolic genes and mineralization of 3-MB, the exconjugant O/T recover ed and displayed high desulphonation activity, thus allowing sequentia l breakdown of both substrates. Our results clearly extend the express ion range of the TOL catabolic genes, but not the replication ability of the plasmid, to the genus Alcaligenes.