MICROBIAL-DEGRADATION OF CHLOROAROMATICS - USE OF THE META-CLEAVAGE PATHWAY FOR MINERALIZATION OF CHLOROBENZENE

Pseudomonas putida GJ31 is able to simultaneously grow on toluene and chlorobenzene. When cultures of this strain were inhibited with 3-fluo rocatechol while growing on toluene or chlorobenzene, 3-methylcatechol or 3-chlorocatechol, respectively, accumulated in the medium. To esta blish the catabolic routes for these catechols, activities of enzymes of the (modified) ortho- and meta-cleavage pathways were measured in c rude extracts of cells of P. putida GJ31 grown an various aromatic sub strates, including chlorobenzene. The enzymes of the modified ortho-cl eavage pathway were never present, while the enzymes of the meta-cleav age pathway were detected in all cultures. This indicated that chloroa romatics and methylaromatics are both converted via the meta-cleavage pathway. Meta cleavage of 3-chlorocatechol usually leads to the format ion of a reactive acylchloride, which inactivates the catechol 2,3-dio xygenase and blocks further degradation of catechols. However, partial ly purified catechol 2,3-dioxygenase of P. putida GJ31 converted 3-chl orocatechol to 2-hydroxy-cis,cis-muconic acid, Apparently, P. putida G J31 has a meta-cleavage enzyme which is resistant to inactivation by t he acylchloride, providing this strain with the exceptional ability to degrade both toluene and chlorobenzene ria the meta-cleavage pathway.