Résumé
Pseudomonas (diff) spp. was isolated from a complex petrochemical sludge, using benzoate as the sole source of carbon. The organism could metabolize 3-chlorobenzoate, releasing approximately 30% of organically bound chloride. 3-Chlorodihydrodihydroxybenzoate and 3-chlorocatechol were confirmed as pathway intermediates by mass spectral and HPLC analysis. About 3-fold higher levels of catechol 1,2-oxygenase were detected in cells grown on 3-chlorobenzoate as compared to that of benzoate. 3-Chlorocatechol inhibited the catechol 1,2-oxygenase activity, when used as assay substrate. A 15-fold purified catechol 1,2-oxygenase had a Km of 0.37 mumole and Vmax of 2.3 with 3-chlorocatechol. Catechol gave Km of 0.2 mumole and Vmax of 40, suggesting that 3-chlorocatechol is not metabolised further and hence blocks the metabolic pathway for 3-chlorobenzoate degradation. In contrast catechol 1,2-oxygenase was not inhibited by 4-chlorocatechol and probably is an intermediate for the total/complete degradation of 3-chlorobenzoate (approx. 30%).