Comparison of 1,2-dichloroethane, dichloroethene and vinyl chloride carbon stable isotope fractionation during dechlorination by two Dehalococcoides strains

• Identical carbon stable isotope fractionation during 1,2-DCA dechlorination for two Dehalococcoides strains.
• Carbon stable isotope fractionation of VC and DCE dechlorination by Dehalococcoides is variable.
• Ethene is a main product of 1,2-DCA dichloroelimination with VC as minor product likely as result of branching.
• Dehalococcoides strain BTF08 specific isotope fractionation of cis-DCE correlates with former reports from a wetland.

Carbon stable isotope fractionation during 1,2-dichloroethane (1,2-DCA), dichloroethene (DCE) and vinyl chloride (VC) dechlorination was analysed for two Dehalococcoides strains, Dehalococcoides mccartyi strain 195 (formerly Dehalococcoides ethenogenes strain 195) and D. mccartyi strain BTF08, and used to characterize the reaction. The isotope enrichment factors (εC) determined for 1,2-DCA were −30.8 ± 1.3‰ and −29.0 ± 3.0‰ for D. mccartyi strain BTF08 and D. mccartyi strain 195, respectively. Enrichment factors (εC) determined for chlorinated ethenes with strain BTF08 were −28.8 ± 1.5‰ (VC), −30.5 ± 1.5‰ (cis-DCE) and −12.4 ± 1.1‰ (1,1-DCE). Product, ethene, related enrichment factors (εC1,2-DCA-ethene) calculated for 1,2-DCA (−34.1 and −32.3‰ for strain BTF08 and strain 195, respectively) were similar to substrate based enrichment factors (εC1,2-DCA), supporting the hypothesis that ethene is the direct product of 1,2-DCA dichloroelimination but that VC was a side product as result of branching in the reaction.

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