Impacts of microbial community composition on isotope fractionation during reductive dechlorination of tetrachloroethylene

Abstract

Isotope fractionation has been used with increasing frequency as a tool to quantify degradation of chlorinated aliphatic pollutants in the environment. The objective of this research was to determine if the electron donor present in enrichment cultures prepared from uncontaminated sediments influenced the extent of isotope fractionation of tetrachloroethylene (PCE), either directly, or through its influence on microbial community composition. Two PCE-degrading enrichment cultures were prepared from Duck Pond (DP) sediment and were incubated with formate (DPF) or H(2) (DPH) as electron donor. DPF and DPH were significantly different in both product distribution and extent of isotope fractionation. Chemical and isotope analyses indicated that electron donors did not directly affect the product distribution or the extent of isotope fractionation for PCE reductive dechlorination. Instead, restriction fragment length polymorphism (RFLP) and sequence analysis of the 16S rRNA clone libraries of DPF and DPH identified distinct microbial communities in each enrichment culture, suggesting that differences in microbial communities were responsible for distinct product distributions and isotope fractionation between the two cultures. A dominant species identified only in DPH was closely related to known dehalogenating species (Sulfurospirillum multivorans and Sulfurospirillum halorespirans) and may be responsible for PCE degradation in DPH. Our study suggests that different dechlorinators exist at the same site and can be preferentially stimulated by different electron donors, especially over the long-term (i.e., years), typical of in-situ ground water remediation.

Effects of electron donors on anaerobic microbial debromination of polybrominated diphenyl ethers (PBDEs)

“…4). Within these six bands, Band I and S are related with the bacteria involved in dechlorination (Dong et al 2011;Rowe et al 2008), Band Q and R are associated with Pseudomonas spp., Band A is associated with uncultured Acidobacteria clone 356G isolated from hydrocarbon contamination soil, while Band D is closely related with Acetoanaerobium noterae strain ATCC 35199. Band F and band G, associated with Alcaligenes sp.…”

Effects of 1,1,1-trichloroethane on enzymatic activity and bacterial community in anaerobic microcosm form sequencing batch reactors

“…Band 9 had high similarity (99%) to bacteria DCE25 (AJ249227), which had an average dechlorination rate of 7.6 mmol/(g VSS) day, with a maximum dechlorination rate of 28.3 mmol/(g VSS) day (Middeldorp et al 2010). Band 10 had a high similarity (100%) to bacterial clone DPHB06 (GQ377116), which came from PCE-degrading enrichment cultures found in Duck Pond sediment (Dong et al 2011). The appearance of the strains represented by the bands 7, 9, and 10 in conjunction with TCA exposure indicated that TCA degrading strains were enriched in the anaerobic culture system (Figs.…”

“…The initially dominant Proteobacteria and Bacteroidetes species (bands 1, 2, 4, 5 and 6) decreased or disappeared, while species belonging to the phyla Proteobacteria, Spirochaetes, Firmicutes, and Bacteroidetes became dominant species (bands 7, 8, 10, 12, 13, 14 and 15) when enriched by TCA exposure in toluene degrading condition. The newly enriched species, bands 7 and 10, belonged to phyla Clostridium and Bacterium with TCA-degrading capabilities (Dong et al 2011;Ziv-El et al 2011), which might be the functional populations in the ASBR system. Under methanogenic conditions, more bands and types of bacteria appeared than in the control.…”

“…The dominant Bacteroidetes and Proteobacteria species (bands 2, 3 and 6) decreased, while species belonging to the phyla Proteobacteria and Bacteroidetes became dominant (bands 1, 4 and 10) in nitrate-reducing condition. The newly enriched species identified from band 10 belonged to a bacterial strain encoding TCA-degrading capabilities (Dong et al 2011), which might be a functional populations in the anaerobic culture system. In sulfate-reducing condition, the initially dominant Bacteroidetes and Proteobacteria species (bands 2, 3, 4 and 5) decreased or disappeared, while species belonging to the phyla Firmicutes and Bacteroidetes became the dominant (bands 7, 10, 11, 12 and 13).…”

Site-specific pre-evaluation of bioremediation technologies for chloroethene degradation

“…However, native dechlorinators stimulated in this study showed greater electron donor versatility towards acetate and H 2 , indicating that an ecological niche in a well-controlled laboratory environment existed for organisms that could derive energy from the complete dechlorination of chlorinated solvents to ethene. To date, there is limited evidence using laboratory mixed cultures indicating that there might be organisms other than Dhc that can synergistically sustain complete reduction in PCE to ethene (Dong et al 2011;Lee et al 2011). …”