Reductive dechlorination of TCE by chemical model systems in comparison to dehalogenating bacteria: Insights from dual element isotope analysis ( 13C/12C, 37Cl/35Cl)

Stefan Cretnik, Kristen A. Thoreson, Anat Bernstein, Karin Ebert, Daniel Buchner, Christine Laskov, Stefan Haderlein, Orfan Shouakar-Stash, Sarah Kliegman, Kristopher McNeill, Martin Elsner

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Abstract

Chloroethenes like trichloroethene (TCE) are prevalent environmental contaminants, which may be degraded through reductive dechlorination. Chemical models such as cobalamine (vitamin B12) and its simplified analogue cobaloxime have served to mimic microbial reductive dechlorination. To test whether in vitro and in vivo mechanisms agree, we combined carbon and chlorine isotope measurements of TCE. Degradation-associated enrichment factors εcarbon and εchlorine (i.e., molecular-average isotope effects) were -12.2‰ ± 0.5‰ and -3.6‰ ± 0.1‰ with Geobacter lovleyi strain SZ; -9.1‰ ± 0.6‰ and -2.7‰ ± 0.6‰ with Desulfitobacterium hafniense Y51; -16.1‰ ± 0.9‰ and -4.0‰ ± 0.2‰ with the enzymatic cofactor cobalamin; -21.3‰ ± 0.5‰ and -3.5‰ ± 0.1‰ with cobaloxime. Dual element isotope slopes m = Δδ13C/ Δδ37Cl ≈ εcarbonchlorine of TCE showed strong agreement between biotransformations (3.4 to 3.8) and cobalamin (3.9), but differed markedly for cobaloxime (6.1). These results (i) suggest a similar biodegradation mechanism despite different microbial strains, (ii) indicate that transformation with isolated cobalamin resembles in vivo transformation and (iii) suggest a different mechanism with cobaloxime. This model reactant should therefore be used with caution. Our results demonstrate the power of two-dimensional isotope analyses to characterize and distinguish between reaction mechanisms in whole cell experiments and in vitro model systems.

Original languageEnglish (US)
Pages (from-to)6855-6863
Number of pages9
JournalEnvironmental Science and Technology
Volume47
Issue number13
DOIs
StatePublished - Jul 2 2013

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    Cretnik, S., Thoreson, K. A., Bernstein, A., Ebert, K., Buchner, D., Laskov, C., Haderlein, S., Shouakar-Stash, O., Kliegman, S., McNeill, K., & Elsner, M. (2013). Reductive dechlorination of TCE by chemical model systems in comparison to dehalogenating bacteria: Insights from dual element isotope analysis ( 13C/12C, 37Cl/35Cl). Environmental Science and Technology, 47(13), 6855-6863. https://doi.org/10.1021/es400107n