Bacterial community analysis of shallow groundwater undergoing sequential anaerobic and aerobic chloroethene biotransformation

Abstract

At Department of Energy Site 300, beneficial hydrocarbon cocontaminants and favorable subsurface conditions facilitate sequential reductive dechlorination of trichloroethene (TCE) and rapid oxidation of the resultant cis-dichloroethene (cis-DCE) upon periodic oxygen influx. We assessed the geochemistry and microbial community of groundwater from across the site. Removal of cis-DCE was shown to coincide with oxygen influx in hydrocarbon-containing groundwater near the source area. Principal component analysis of contaminants and inorganic compounds showed that monitoring wells could be differentiated based upon concentrations of TCE, cis-DCE, and nitrate. Structurally similar communities were detected in groundwater from wells containing cis-DCE, high TCE, and low nitrate levels. Bacteria identified by sequencing 16S rRNA genes belonged to seven phylogenetic groups, including Alpha-, Beta-, Gamma- and Deltaproteobacteria, Nitrospira, Firmicutes and Cytophaga-Flexibacter-Bacteroidetes (CFB). Whereas members of the Burkholderiales and CFB group were abundant in all wells (10(4)-10(9) 16S rRNA gene copies L(-1)), quantitative PCR showed that Alphaproteobacteria were elevated (>10(6) L(-1)) only in wells containing hydrocarbon cocontaminants. The study shows that bacterial community structure is related to groundwater geochemistry and that Alphaproteobacteria are enriched in locales where cis-DCE removal occurs.

A Long-Term Field Study of In Situ Bioremediation in a Fractured Conglomerate Trichloroethene Source Zone

“…There is little evidence of anaerobic TCE biodegradation, except for occasional detection of small amounts of 1,2-dichloroethene (DCE) (<2 mg/L). This is consistent with a previous molecular biological study (Miller, Franklin, and Halden 2007), which found Dehalococcoides were absent in groundwater from this site, and a separate microcosm study, in which dechlorination stopped at DCE after 4 months of incubation with various substrates (data not shown).…”

“…The vcrA gene indicative of Dehalococcoides was detected in wells where ethene was present (W-1825, W-T2), whereas it was not detected in well W-1833 where ethene was absent (Figure 7a, b). Given the absence of Dehalococcoides at this site prior to this study (Miller, Franklin, and Halden 2007), the detection of the vcrA gene possessed by the KB-1 consortium (Waller et al 2005) after bioaugmentation strongly suggests that bioaugmenation was responsible for the observed ethene production.…”

“…(M€ uller et al 2004). The vcrA gene was a good target for the present test because it is present in the consortium constituting the KB-1 bioaugmentation culture (Waller et al 2005) and was absent at this site prior to bioaugmentation (Miller, Franklin, and Halden 2007).…”

Elucidating carbon uptake from vinyl chloride using stable isotope probing and Illumina sequencing

“…This phylum (Firmicutes) has not yet been associated with VCassimilation but has been previously reported in sites contaminated with chlorinated solvents (Miller et al 2007). …”

Biodegradation of vinyl chloride, cis-dichloroethene and 1,2-dichloroethane in the alkene/alkane-oxidising Mycobacterium strain NBB4

“…However, these anaerobic processes may fail to go to completion, resulting in accumulation of more-hazardous compounds such as VC. For this reason, there is great interest in investigating the potential of aerobic bacteria for bioremediation of the lesser-chlorinated ethenes and ethanes-this would allow sequential anaerobic-aerobic treatment for complete pollutant removal (Miller et al 2007).…”