Microbial transformation of chlorinated benzoates

摘要

Chlorinated benzoates enter the environment through their use as herbicides or as metabolites of other halogenated compounds. Ample evidence is available indicating biodegradation of chlorinated benzoates to CO2 and chloride in the environment under aerobic as well as anaerobic conditions. Under aerobic conditions, lower chlorinated benzoates can serve as sole electron and carbon sources supporting growth of a large list of taxonomically diverse bacterial strains. These bacteria utilize a variety of pathways ranging from those involving an initial degradative attack by dioxygenases to those initiated by hydrolytic dehalogenases. In addition to mono-chlorinated benzoates, several bacterial strains have been isolated that can grow on dichloro-, and triehloro- isomers of chlorobenzoates. Some aerobic bacteria are capable of cometabolizing chlorinated benzoates with simple primary substrates such as benzoate. Under anaerobic conditions, chlorinated benzoates are subject to reductive dechlorination when suitable electron-donating substrates are available. Several halorespiring bacteria are known which can use chlorobenzoates as electron acceptors to support growth. For example, Desulfomonile tiedjei catalyzes the reductive dechlorination of 3-chloro-benzoate to benzoate. The benzoate skeleton is mineralized by other microorganisms in the anaerobic environment. Various dichloro- and trichloro-benzoates are also known to be dechlorinated in anaerobic sediments.