Journal Article

Microbial oxidation of 1,2-dichloroethane under anoxic conditions with nitrate as electron acceptor in mixed and pure cultures

Mary Joyce Dinglasan-Panlilio, Sandra Dworatzek, Scott Mabury and Elizabeth Edwards

in FEMS Microbiology Ecology

Volume 56, issue 3, pages 355-364
Published in print June 2006 |
Published online February 2006 | e-ISSN: 1574-6941 | DOI: http://dx.doi.org/10.1111/j.1574-6941.2006.00077.x

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Abstract

Many organisms have been found to readily oxidize the prevalent contaminant 1,2-dichloroethane (1,2-DCA) to CO2 under aerobic conditions. Some organisms have also been isolated that can reduce 1,2-DCA to ethene via dihaloelimination under anaerobic, fermentative conditions. However, none have been described that can metabolize 1,2-DCA under anoxic, nitrate-reducing conditions. In microcosms prepared from aquifer material and groundwater samples from a contaminated site in eastern Louisiana, USA, 1,2-DCA was observed to degrade with nitrate as the terminal electron acceptor. Nitrate-dependent enrichment cultures were developed from these microcosms that sustained rapid 1,2-DCA degradation rates of up to 500 μM day−1. This degradation was tightly coupled to complete reduction of nitrate via nitrite to nitrogen gas. A novel 1,2-DCA-degrading organism belonging to the Betaproteobacteria (affiliated with the genus Thauera) was isolated from this enrichment culture. However, degradation rates were much slower in cultures of the isolate than observed in the parent mixed culture. Complete mineralization of 1,2-DCA to CO2 was linked to cell growth and to nitrate reduction in both enrichment and isolated cultures. Monochloroacetate, a putative metabolite of 1,2-DCA degradation, could also be mineralized by these cultures.

Keywords: 1,2-dichloroethane; biodegradation; nitrate reducing conditions; anaerobic; pure culture

Journal Article.  5371 words.  Illustrated.

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