ENZYMOLOGY OF THE DEGRADATION OF (DI)CHLOROBENZENES BY XANTHOBACTER-FLAVUS 14P1

Xanthobacter flavus 14p1 used 1,4,-dichlorobenzene as the sole source of carbon and energy but did not grow on other (chloro)aromatic compou nds. 1,4-Dichlorobenzene was attacked by a chlorobenzene dioxygenase, and the intermediate chlorocatechol was metabolized by the modified ol tho pathway. All enzymes necessary to convert 1,4-dichlorobenzene to 3-oxoadipate showed a low substrate specificity and also accepted the respective intermediates of chlorobenzene or 1,3-dichlorobenzene degra dation. Of the three compounds chlorobenzene, 1,4-dichlorobenzene, and 1,3-dichlorobenzene, the latter was the most toxic for X. flavus 14p1 . Furthermore, 1,3-dichlorobenzene did not induce chlorocatechol 1,2-d ioxygenase activity of the organism. Chlorobenzene, however, induced c hlorocatechol 1,2-dioxygenase, dienelactone hydrolase, and maleylaceta te reductase activities. As demonstrated by chloride release, also chl orobenzene dioxygenase, chlorobenzene cis-dihydrodiol dehydrogenase, a nd chloromuconate cycloisomerase activities were present in chlorobenz ene-induce cells, but chlorobenzene failed to support growth. Presumab ly a toxic compound was formed from one of the intermediates.