Metabolism of 3-chloro-, 4-chloro-, and 3,5-dichlorobenzoate by a pseudomonad

Abstract

Pseudomonas sp. WR912 was isolated by continuous enrichment in 3 steps with 3-chloro-, 4-chloro- and finally 3,5-dichlorobenzoate as sole source of C and energy. The doubling times of the pure culture with these growth substrates were 2.6, 3.3 and 5.2 h, respectively. Stoichiometric amounts of chloride were eliminated during growth. O2 uptake rates with chlorinated benzoates revealed low stereospecificity of the initial benzoate 1,2-dioxygenation. Dihydrodihydroxybenzoate dehydrogenase, catechol 1,2-dioxygenase and muconate cycloisomerase activities were found in cell-free extracts. The ortho cleavage activity for catechols appeared to involve induction of isoenzymes with different stereospecificity towards chlorocatechols. A catabolic pathway for chlorocatechols was proposed on the basis of similarity to chlorophenoxyacetate catabolism, and cometabolism of 3,5-dimethylbenzoate by chlorobenzoate-induced cells yielded 2,5-dihydro-2,4-dimethyl-5-oxo-furan-2-acetic acid.