CHARACTERIZATION OF CATECHOL-DEGRADING AND CHLOROCATECHOL-DEGRADING ACTIVITY IN THE ORTHO-CHLORINATED BENZOIC ACID-DEGRADING PSEUDOMONAS SP. CPE2 STRAIN

Pyrocatechase activity was studied in the Pseudomonas sp. CPE2 strain, which is capable of growing on 2-chlorobenzoic and 2,5-dichlorobenzoi c acid, giving rise to catechol and 4-chlorocatechol, respectively, as intermediate metabolites. The CPE2 crude extract was found to metabol ize both catechol and 4-chlorocatechol. Enzymatic as well as phenotypi c studies performed both on this strain and on a mutant strain lacking the chlorocatechol-degrading genes were consistent with the presence of two catechol-cleaving enzymes, one active mainly against catechol ( pyrocatechase I) and the other with broader substrate specificity (pyr ocatechase II). The latter enzyme also appeared to be induced when CPE 2 cells were grown on 2-chlorobenzoic acid, thus contributing to catec hol metabolism, in addition to pyrocatechase I. Despite the presence o f a large plasmid in CPE2 cells, the chlorocatechol-degrading genes, h ighly homologous to the de operon, were located on the chromosome. Th selection at relatively high frequency of mutant strains with altered growth capabilities and which lacked the chlorocatechol-degrading gene s suggests a transposon-like character for these catabolic genes in th e CPE2 strain.