Over the past few decades, the extensive use of chlorinated benzenes has led to considerable release of these compounds into the environment. Since chlorinated benzenes are chemically stable in nature, biological degradation is the only process by which these compounds are eliminated.
1,4-Dichlorobenzene is a colorless solid with a mothball-like odor. It is used as moth repellent, general insecticide, pesticide, air deodorant and chemical intermediate for dyes. It is moderately toxic to humans. It is a priority environmental pollutant listed by the Environmental Protection Agency.
1,4-Dichlorobenzene can be degraded under aerobic conditions. Xanthobacter flavus 14pl uses 1,4-dichlorobenzene as the sole source of carbon and energy but does not grow on other (chloro)aromatic compounds. 1,4-Dichlorobenzene is attacked by chlorobenzene dioxygenase, and after rearomatization, the resulting dichlorocatechol is degraded via a modified ortho pathway, as described by Sommer & Gorisch (1997). Pure cultures of Sphingomonas haloaromaticamans and some Pseudomonas species can degrade 1,4-dichlorobenzene through similar pathways.
Under anaerobic conditions, some methanogenic microbial consortia are able to transform 1,4-dichlorobenzene by reductive dechlorination via monochlorobenzene to unsubstituted benzene, as shown in the 1,2,4-Trichlorobenzene Pathway.
The following is a text-format 1,4-dichlorobenzene pathway map. Organisms which can initiate the pathway are given, but other organisms may also carry out later steps. Follow the links for more information on compounds or reactions. This map is also available in graphic (9k) format.
1,4-Dichlorobenzene Xanthobacter flavus 14pl Sphingomonas haloaromaticamans Pseudomonas sp. | | chlorobenzene | dioxygenase | | V 3,6-Dichloro-cis- 1,2-dihydroxycyclohexa-3,5-diene | | chlorobenzene | cis-dihydrodiol | dehydrogenase | V 3,6-Dichlorocatechol | | chlorocatechol | 1,2-dioxygenase | | V 2,5-Dichloro-cis,cis-muconate | | chloromuconate | cycloisomerase | | V trans-2-Chlorodienelactone | | | | | V to the 2,4-dichlorophenoxyacetic Acid Pathway
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