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Anaerobic benzene biodegradation--a new era
John D Coates1, Romy Chakraborty, Michael J McInerney
1Department of Plant and Microbial Biology, University College Berkeley, Berkeley, CA 94720, USA. jcoates@micro.siu.edu
Research in Microbiology
|February 1, 2003
Summary
Anaerobic benzene degradation remains unclear, but phenol and benzoate are key intermediates. Evidence suggests potential alkylation mechanisms, possibly involving corrinoid enzymes, though diverse pathways may exist.
Area of Science:
- Environmental Microbiology
- Biochemistry
- Organic Chemistry
Background:
- Benzene biodegradation occurs anaerobically, but the specific mechanisms are not fully understood.
- Phenol and benzoate are consistently identified as intermediates, suggesting hydroxylation as an initial step.
Purpose of the Study:
- To elucidate the biochemical pathways involved in anaerobic benzene degradation.
- To investigate potential mechanisms, including hydroxylation and alkylation, and their supporting evidence.
Main Methods:
- Analysis of intermediate products (phenol, benzoate) during anaerobic benzene degradation.
- 13C-labeling studies to trace carbon origins.
- Investigating the effects of cofactors (vitamin B12) and inhibitors (propyl iodide) on degradation rates.
Main Results:
- Phenol and benzoate are confirmed intermediates, with benzoate's carboxyl carbon originating from benzene.
- Fumarate addition is unlikely due to benzene's high activation energy.
- Degradation by Dechloromonas strain RCB is stimulated by vitamin B12 and inhibited by propyl iodide, suggesting corrinoid enzyme involvement.
Conclusions:
- The initial step may involve benzene hydroxylation to phenol, followed by conversion to benzoate.
- Alkylation of benzene to toluene is a plausible alternative mechanism, supported by enzyme cofactor studies.
- Diverse anaerobic benzene degradation pathways may be employed by different microorganisms.