Abstract
Thus far, members of the genus Dehalo- coccoides are the only microorganisms known to dehalogenate chlorinated ethenes to ethene and thereby detoxify these common groundwater pollutants. Therefore, it is important to characterize the taxonomic and functional diversity of these key microorganisms and their reductive dehalogenase (RDase) genes in contaminated aquifers for assessing the natural attenuation potential. Little is known about the diversity of RDase genes under field conditions or in laboratory systems under selective pressure during de- chlorination activities. Here, we evaluate the diversity of Dehalococcoidessp. and three RDase genes in groundwater as well as in water from a constructed wetland and micro- cosms setup with contaminated groundwater from the same field site in Bitterfeld (Saxony-Anhalt, Germany). The pres- ence and relative abundance of Pinellas and Cornell sub- groups of Dehalococcoides was evaluated by a novel direct sequencing method, which revealed that all sequences were identical and affiliated to the Pinellas subgroup. Contrarily, our results showed remarkable differences at the functional gene level between the systems. Of the vinyl chloride reductase genes, vcrA was detected in samples from the groundwater, wetland, and microcosms, whereas bvcAwas only found in wetland and microcosm samples. The trichloroethene dehalogenase gene, tceA could not be de- tected at all, although complete dehalogenation activity of higher chlorinated ethenes was observed. Our study dem- onstrates that although the Dehalococcoides 16S rRNA gene sequences retrieved from the investigated systems were identical, the RDase gene diversity varied among the systems, according to the spectrum of the chlorinated eth- enes present.
Published Version
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