COMAMONAS-ACIDOVORANS UCC61 CATABOLIZES O-PHTHALATE VIA A 4,5-OXYGENATION PATHWAY THAT IS ENCODED ON A 70 KBP SECTION OF PLASMID POPH1 BOUNDED BY DIRECTLY REPEATED SEQUENCES

Twenty-three bacteria capable of growing with o-phthalate as sole carb on source were isolated from sewage sludge. One of these, named UCC61, was identified as a strain of Comamonas acidovorans and was selected for further study. UCC61 was found to carry a single plasmid (named pO PH1) of about 270 kbp in size. The phthalate-utilizing phenotype of UC C61 was unstable and could be lost either by complete curing of pOPH1, or by the deletion of a specific 70 kbp segment from pOPH1. This segm ent, termed the Pht element, was extensively restriction mapped (using four restriction endonucleases), and was found to be flanked by direc tly repeated sequences greater than 1.9 kbp in length. Data from compa rative restriction analysis of pOPH1 and its deleted derivative were c onsistent with a deletion mechanism that involves homologous recombina tion between the direct repeats. UCC61 was found to catabolize o-phtha late via 4,5-oxygenation, dehydrogenation and decarboxylation to proto catechuate. These three activities were encoded within the Pht element , with the genes clustered near the right-hand terminus. Protocatechua te metabolism was chromosomally encoded, as also was the ability to ca tabolize the m- and p-isomers of phthalate.