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Applied and Environmental Microbiology, April 2007, p. 2513-2521, Vol. 73, No. 8
0099-2240/07/$08.00+0     doi:10.1128/AEM.02909-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

The Dehalococcoides Population in Sediment-Free Mixed Cultures Metabolically Dechlorinates the Commercial Polychlorinated Biphenyl Mixture Aroclor 1260{triangledown}

Donna L. Bedard,1* Kirsti M. Ritalahti,2 and Frank E. Löffler2,3

Department of Biology, Rensselaer Polytechnic Institute, Troy, New York 12180,1 School of Civil and Environmental Engineering,2 School of Biology, Georgia Institute of Technology, Atlanta, Georgia 303323

Received 16 December 2006/ Accepted 9 February 2007

Microbial reductive dechlorination of commercial polychlorinated biphenyl (PCB) mixtures (e.g., Aroclors) in aquatic sediments is crucial to achieve detoxification. Despite extensive efforts over nearly two decades, the microorganisms responsible for Aroclor dechlorination remained elusive. Here we demonstrate that anaerobic bacteria of the Dehalococcoides group derived from sediment of the Housatonic River (Lenox, MA) simultaneously dechlorinate 64 PCB congeners carrying four to nine chlorines in Aroclor 1260 in the sediment-free JN cultures. Quantitative real-time PCR showed that the Dehalococcoides cell titer in JN cultures amended with acetate and hydrogen increased from 7.07 x 106 ± 0.42 x 106 to 1.67 x 108 ± 0.04 x 108 cells/ml, concomitant with a 64.2% decrease of the PCBs with six or more chlorines in Aroclor 1260. No Dehalococcoides growth occurred in parallel cultures without PCBs. Aroclor 1260 dechlorination supported the growth of 9.25 x 108 ± 0.04 x 108 Dehalococcoides cells per µmol of chlorine removed. 16S rRNA gene-targeted PCR analysis of known dechlorinators (i.e., Desulfitobacterium, Dehalobacter, Desulfuromonas, Sulfurospirillum, Anaeromyxobacter, Geobacter, and o-17/DF-1-type Chloroflexi organisms) ruled out any involvement of these bacterial groups in the dechlorination. Our results suggest that the Dehalococcoides population present in the JN cultures also catalyzes in situ dechlorination of Aroclor 1260 in the Housatonic River. The identification of Dehalococcoides organisms as catalysts of extensive Aroclor 1260 dechlorination and our ability to propagate the JN cultures under defined conditions offer opportunities to study the organisms' ecophysiology, elucidate nutritional requirements, identify reductive dehalogenase genes involved in PCB dechlorination, and design molecular tools required for bioremediation applications.

* Corresponding author. Mailing address: Department of Biology, SC 1W14, Rensselaer Polytechnic Institute, 110 8th St., Troy, NY 12180. E-mail: bedard{at}rpi.edu

{triangledown} Published ahead of print on 16 February 2007.

Applied and Environmental Microbiology, April 2007, p. 2513-2521, Vol. 73, No. 8
0099-2240/07/$08.00+0     doi:10.1128/AEM.02909-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Adrian, L., Dudkova, V., Demnerova, K., Bedard, D. L. (2009). "Dehalococcoides" sp. Strain CBDB1 Extensively Dechlorinates the Commercial Polychlorinated Biphenyl Mixture Aroclor 1260. Appl. Environ. Microbiol. 75: 4516-4524 [Abstract] [Full Text]  
  • Rowe, A. R., Lazar, B. J., Morris, R. M., Richardson, R. E. (2008). Characterization of the Community Structure of a Dechlorinating Mixed Culture and Comparisons of Gene Expression in Planktonic and Biofloc-Associated "Dehalococcoides" and Methanospirillum Species. Appl. Environ. Microbiol. 74: 6709-6719 [Abstract] [Full Text]  
  • Johnson, D. R., Brodie, E. L., Hubbard, A. E., Andersen, G. L., Zinder, S. H., Alvarez-Cohen, L. (2008). Temporal Transcriptomic Microarray Analysis of "Dehalococcoides ethenogenes" Strain 195 during the Transition into Stationary Phase. Appl. Environ. Microbiol. 74: 2864-2872 [Abstract] [Full Text]  


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