Microbial composition of chlorinated ethene-degrading cultures dominated by Dehalococcoides

Abstract

The community composition of microbial cultures degrading tetrachloroethene (PCE), trichloroethene (TCE), cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC) to ethene was studied. A combination of PCR-denaturing gradient gel electrophoresis (PCR-DGGE) and 16S rRNA gene sequence analysis revealed that all cultures contained Dehalococcoides populations, but that the populations of other organisms varied widely. Based on the sequences of cloned 16S rRNA genes, real-time PCR methods were developed for several of these phylotypes affiliated with the putative dechlorinators Sulfurospirillum and Geobacter, the putative methanogens Methanomethylovorans, Methanomicrobiales, Methanosaeta and Methanosarcina, the putative acetogens Acetobacterium, Spirochaetes, and Sporomusa, and the putative fermenters Bacteroidetes, Syntrophus, and Syntrophobacter. These novel quantitative PCR methods were then used to estimate relative abundances of each phylotype in several individual cultures maintained on each chlorinated ethene. Dehalococcoides populations were the dominant phylotypes assayed in most KB-1 cultures, agreeing with the DGGE and cloning results. A Geobacter phylotype was also strongly represented in most PCE and TCE cultures, but not in cDCE or VC cultures, suggesting a possible role for this organism as a PCE-to-cDCE dechlorinator. The Sulfurospirillum phylotype was estimated to comprise a minor fraction of 16S rRNA gene copies and did not appear to have an important role in dechlorination.

The reactive transport of trichloroethene is influenced by residence time and microbial numbers

“…Quantification of Dehalococcoides numbers was performed using real-time PCR as described previously (Dijk et al 2008) with a detection limit of 1.6×10 6 16S rDNA copies L -1 . Following the same protocol, Geobacter and Bacteria numbers were quantified in duplicate using the ABsolute TM QPCR SYBR Green Mix (ABgene) and primer sets Geo73f/Geo485r (Duhamel and Edwards, 2006) and Eub341F/Eub534r (Muyzer et al 1993), respectively (see supporting information). Microbial numbers were measured in the effluent (and pore water) of the column treatment at seven (five) times during the experiment.…”

Metagenomic analysis of a stable trichloroethene-degrading microbial community

“…Based on the median contig length and average read depth of Spirochete contigs (Table 2) however, the Spirochete appears to be one of the more abundant organisms in ANAS. Studies of other Dhc-containing dechlorinating microbial communities have also detected Spirochetes (Gu et al, 2004;Macbeth et al, 2004;Duhamel and Edwards, 2006). Based on what is known of Spirochetes in general, they may be fermenters or homoacetogens in these communities (Leadbetter et al, 1999;Madigan et al, 2008).…”

Evaluating the fate of chlorinated ethenes in streambed sediments by combining stable isotope, geochemical and microbial methods

“…Different methods have been proposed to evaluate the occurrence of complete reductive dechlorination of chlorinated ethenes including: 1) characterization of geochemical conditions (availability of electron donors such as H 2 , Luijten et al, 2004; assessment of redox conditions, Witt et al, 2002;Lu et al, 2006), 2) characterization of parent and daughter product patterns (Witt et al, 2002) and 3) assessment of the presence and activity of key organisms such as Dehalococcoides (Fennell et al, 2001;Hendrickson et al, 2002;Müller et al, 2004;Duhamel and Edwards, 2006;Rahm and Richardson, 2008;Imfeld et al, 2008;Lee et al, 2008). While geochemical conditions and the presence of certain organisms can indicate whether the conditions are favorable for reductive dechlor-ination, these parameters usually do not provide information about the degree of transformation.…”