Detection and Quantification of Dehalococcoides-Related Bacteria in a Chlorinated Ethene-Contaminated Aquifer Undergoing Natural Attenuation |
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Authors: | Helmut Bürgmann Jutta Kleikemper Laurence Duc Michael Bunge Martin H Schroth Josef Zeyer |
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Institution: | 1. Institute of Biogeochemistry and Pollutant Dynamics , Swiss Federal Institute of Technology Zurich (ETHZ) , Zurich, Switzerland;2. Centre of Ecology, Evolution and Biogeochemistry , Eawag, Swiss Federal Institute of Aquatic Science and Technology , Kastanienbaum, Switzerland;3. Institute of Biogeochemistry and Pollutant Dynamics , Swiss Federal Institute of Technology Zurich (ETHZ) , Zurich, Switzerland |
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Abstract: | Detection and quantification of bacteria related to Dehalococcoides is essential for the development of effective remediation strategies for tetrachloroethene (PCE)-contaminated sites. In this study, the authors applied three methods for quantifying Dehalococcoides-like bacteria in a PCE-contaminated aquifer undergoing natural attenuation in Grenchen, Switzerland: a catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) protocol, a competitive nested polymerase chain reaction (PCR) approach, and a direct PCR end point quantification with external standards. For the investigated aquifer, multiple lines of evidence indicated that reductive dechlorination (and likely dehalorespiration) was an active process. Both PCR-based quantification methods indicated that low numbers of mostly sediment-bound Dehalococcoides were present in the contaminated zone of the Grenchen aquifer. Estimates based on the quantitative PCR methods ranged from 2.1 × 107 to 1.5 × 108 sediment-bound Dehalococcoides 16S rRNA gene copies per liter of aquifer volume. In contrast, the liquid phase only contained between 8 and 80 copies per liter aquifer volume. CARD-FISH was not sensitive enough for the quantification of Dehalococcoides cell numbers in this aquifer. Cloning and sequencing of the PCR products revealed the presence of sequences closely related to Dehalococcoides isolates such as D. ethenogenes and Dehalococcoides sp. BAV1. An apparently abundant group (termed “Grenchen Cluster”) of sequences more distantly related to Dehalococcoides was also identified, so far without cultured representatives. |
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Keywords: | bioremediation CARD-FISH dehalogenation natural attenuation quantitative PCR |
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