FORMATION OF CHLOROCATECHOL META CLEAVAGE PRODUCTS BY A PSEUDOMONAD DURING METABOLISM OF MONOCHLOROBIPHENYLS

Pseudomonas cepacia P166 was able to metabolize all monochlorobiphenyl s to the respective chlorobenzoates. Although they transiently accumul ated, the chlorobenzoate degradation intermediates were further metabo lized to chlorocatechols, which in turn were meta cleaved. 2- and 3-Ch lorobiphenyl both produced 3-chlorocatechol, which was transformed to an acyl halide upon meta cleavage. 3-Chlorocatechol metabolism was tox ic to the cells and impeded monochlorobiphenyl metabolism. In the case of 2-chlorobiphenyl, toxicity was manifested as a diminished growth r ate, which nevertheless effected rapid substrate utilization. In the c ase of 3-chlorobiphenyl, which generates 3-chlorocatechol more rapidly than does 2-chlorobiphenyl, toxicity was manifested as a decrease in viable cells during substrate utilization. 4-Chlorobenzoate was transf ormed to 4-chlorocatechol, which was metabolized by a meta cleavage pa thway leading to dehalogenation. Chloride release from 4-chlorocatecho l metabolism, however, was slow and did not coincide with rapid 4-chlo rocatechol turnover. Growth experiments with strain P166 on monochloro biphenyls illustrated the difficulties of working with hydrophobic sub strates that generate toxic intermediates. Turbidity could not be used to measure the growth of bacteria utilizing monochlorobiphenyls becau se high turbidities were routinely measured from cultures with very lo w viable-cell counts.