METABOLISM OF CHLOROFLUOROCARBONS AND POLYBROMINATED COMPOUNDS BY PSEUDOMONAS-PUTIDA G786(PHG-2) VIA AN ENGINEERED METABOLIC PATHWAY

The recombinant bacterium Pseudomonas putida G786(pHG-2) metabolizes p entachloroethane to glyoxylate and carbon dioxide, using cytochrome P- 450(CAM) and toluene dioxygenase to catalyze consecutive reductive and oxidative dehalogenation reactions (L. P. Wackett, M. J. Sadowsky, L. N. Newman, H.-G. Hur, and S. Li, Nature [London] 368:627-629, 1994). The present study investigated metabolism of brominated and chlorofluo rocarbon compounds by the recombinant strain. Under anaerobic conditio ns, P. putida G786(pHG-2) reduced 1,1,2,2-tetrabromoethane, 1,2-dibrom o-1,2-dichloroethane, and 1,1,1,2-tetrachloro-2,2-difluoroethane to pr oducts bearing fewer halogen substituents. Under aerobic conditions, P . putida G786(pHG-2) oxidized cis- and trans-1,2-dibromoethenes, 1,1-d ichloro-2,2-difluoroethene, and 1,2-dichloro-1-fluoroethene. Several c ompounds were metabolized by sequential reductive and oxidative reacti ons via the constructed metabolic pathway. For example, 1,1,2,2-tetrab romoethane was reduced by cytochrome P-450(CAM) to 1,2-dibromoethenes, which were subsequently oxidized by toluene dioxygenase. The same pat hway metabolized 1,1,1,2-tetrachloro-2,2-difluoroethane to oxalic acid as one of the final products. The results obtained in this study indi cate that P. putida G786(pHG-2) metabolizes polyfluorinated, chlorinat ed, and brominated compounds and further demonstrates the value of usi ng a knowledge of catabolic enzymes and recombinant DNA technology to construct useful metabolic pathways.