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Dehalorespiration with hexachlorobenzene and pentachlorobenzene by Dehalococcoides sp. strain CBDB1
Gopalakrishnan Jayachandran1, Helmut Görisch, Lorenz Adrian
1Fachgebiet Technische Biochemie, Institut für Biotechnologie, Technische Universität Berlin, Seestrasse 13, Sekr. GG1, 13353 Berlin, Germany.
Archives of Microbiology
|October 18, 2003
Summary
Dehalococcoides sp. strain CBDB1 can dechlorinate hexachlorobenzene and pentachlorobenzene via dehalorespiration when supplied in crystalline form. This study reveals distinct dechlorination pathways and potential induction of specific reductive dehalogenases by different chlorobenzenes.
Area of Science:
- Environmental Microbiology
- Bioremediation
- Anaerobic Respiration
Background:
- Dehalococcoides species are key players in the reductive dechlorination of chlorinated pollutants.
- Previous studies faced challenges in culturing Dehalococcoides sp. strain CBDB1 with highly chlorinated benzenes as electron acceptors.
- Understanding the metabolic capabilities of Dehalococcoides is crucial for developing effective bioremediation strategies.
Purpose of the Study:
- To investigate the ability of Dehalococcoides sp. strain CBDB1 to utilize hexachlorobenzene (HCB) and pentachlorobenzene (PeCB) as electron acceptors.
- To elucidate the reductive dechlorination pathways and end-products for HCB and PeCB by this bacterium.
- To determine the growth yields and potential induction of reductive dehalogenases under these conditions.
Main Methods:
- Cultivation of Dehalococcoides sp. strain CBDB1 with crystalline HCB and PeCB as electron acceptors and hydrogen as the electron donor.
- Analysis of dechlorination products using gas chromatography.
- Measurement of growth yields and reductive dehalogenase activity.
Main Results:
- Dehalococcoides sp. strain CBDB1 successfully grew using crystalline HCB and PeCB, achieving growth yields of 2.1 and 2.9 g protein/mol Cl(-) released, respectively.
- HCB was dechlorinated to PeCB, then to a mixture of 1,2,3,5- and 1,2,4,5-tetrachlorobenzene, with final products including 1,3,5-trichlorobenzene and 1,3-/1,4-dichlorobenzene.
- The study identified two distinct dechlorination pathways, suggesting differential induction of reductive dehalogenases based on the chlorobenzene congener.
Conclusions:
- This is the first report of pure culture dehalorespiration of HCB and PeCB by Dehalococcoides sp. strain CBDB1.
- The organism employs specific pathways for dechlorinating highly chlorinated benzenes, removing doubly flanked chlorines preferentially in one route.
- Findings highlight the potential of Dehalococcoides sp. strain CBDB1 for bioremediating highly chlorinated benzene contamination.