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

1 Department of Pure and Applied Biology, University of Wales, Cardiff, PO Box 915, Cathays Park, Cardiff CF1 3TL, UK ABSTRACT Summary: Twenty-three bacteria capable of growing with o -phthalate as sole carbon 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 pOPH1) of about 270 kbp in size. The phthalate-utilizing phenotype of UCC61 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 segment, termed the Pht element, was extensively restriction mapped (using four restriction endonucleases), and was found to be flanked by directly repeated sequences greater than 1-9 kbp in length. Data from comparative restriction analysis of pOPH1 and its deleted derivative were consistent with a deletion mechanism that involves homologous recombination between the direct repeats. UCC61 was found to catabolize o -phthalate via 4,5-oxygenation, dehydrogenation and decarboxylation to protocatechuate. These three activities were encoded within the Pht element, with the genes clustered near the right-hand terminus. Protocatechuate metabolism was chromosomally encoded, as also was the ability to catabolize the m - and p -isomers of phthalate. 2 Author for correspondence: W. A. Venables. Keywords: Comamonas , phthalate, degradation, plasmid-encoded Present address: Department of Microbiology, Monash University, Clayton, Victoria 3168, Australia. Present address: Department of Microbiology, Molecular Biology and Biochemistry, University of Idaho, Moscow, ID 83844-3052, USA.