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Applied and Environmental Microbiology, May 2007, p. 3009-3018, Vol. 73, No. 9
0099-2240/07/$08.00+0     doi:10.1128/AEM.02958-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Microbial Reductive Dechlorination of Aroclor 1260 in Baltimore Harbor Sediment Microcosms Is Catalyzed by Three Phylotypes within the Phylum Chloroflexi{triangledown}

Sonja K. Fagervold,1 Harold D. May,2 and Kevin R. Sowers1*

Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, Maryland,1 Department of Microbiology and Immunology, Marine Biomedicine & Environmental Science Center, Medical University of South Carolina, Charleston, South Carolina2

Received 20 December 2006/ Accepted 2 March 2007

The specific dechlorination pathways for Aroclor 1260 were determined in Baltimore Harbor sediment microcosms developed with the 11 most predominant congeners from this commercial mixture and their resulting dechlorination intermediates. Most of the polychlorinated biphenyl (PCB) congeners were dechlorinated in the meta position, and the major products were tetrachlorobiphenyls with unflanked chlorines. Using PCR primers specific for the 16S rRNA genes of known PCB-dehalogenating bacteria, we detected three phylotypes within the microbial community that had the capability to dechlorinate PCB congeners present in Aroclor 1260 and identified their selective activities. Phylotype DEH10, which has a high level of sequence identity to Dehalococcoides spp., removed the double-flanked chlorine in 234-substituted congeners and exhibited a preference for para-flanked meta-chlorines when no double-flanked chlorines were available. Phylotype SF1 had similarity to the o-17/DF-1 group of PCB-dechlorinating bacteria. Phylotype SF1 dechlorinated all of the 2345-substituted congeners, mostly in the double-flanked meta position and 2356-, 236-, and 235-substituted congeners in the ortho-flanked meta position, with a few exceptions. A phylotype with 100% sequence identity to PCB-dechlorinating bacterium o-17 was responsible for an ortho and a double-flanked meta dechlorination reaction. Most of the dechlorination pathways supported the growth of all three phylotypes based on competitive PCR enumeration assays, which indicates that PCB-impacted environments have the potential to sustain populations of these PCB-dechlorinating microorganisms. The results demonstrate that the variation in dechlorination patterns of congener mixtures typically observed at different PCB impacted sites can potentially be mediated by the synergistic activities of relatively few dechlorinating species.

* Corresponding author. Mailing address: Center of Marine Biotechnology, University of Maryland Biotechnology Institute, 701 E. Pratt St., Baltimore, MD 21202. Phone: (410) 234-8878. Fax: (410) 234-8896. E-mail: Sowers{at}comb.umbi.umd.edu

{triangledown} Published ahead of print on 9 March 2007.

Applied and Environmental Microbiology, May 2007, p. 3009-3018, Vol. 73, No. 9
0099-2240/07/$08.00+0     doi:10.1128/AEM.02958-06
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]  
  • May, H. D., Miller, G. S., Kjellerup, B. V., Sowers, K. R. (2008). Dehalorespiration with Polychlorinated Biphenyls by an Anaerobic Ultramicrobacterium. Appl. Environ. Microbiol. 74: 2089-2094 [Abstract] [Full Text]  


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