Effects of Bacterial Growth Conditions on Carbon and Chlorine Isotope Fractionation Associated with TCE Biotransformation

Daniel Buchner, Philipp R. Martin, Johannes Scheckenbach, Sebastian Behrens, Stefan B. Haderlein

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Abstract

The variability of reported carbon and chlorine isotope enrichment factors (ϵCand ϵCl) for trichloroethene (TCE) respiration even for pure bacterial cultures limits the applicability of compound-specific isotope analysis (CSIA) for quantitative assessment of TCE biotransformation. As the growth and metabolism of bacteria in the environment can differ substantially from standardized laboratory conditions, we investigated the effects of environmentally relevant variables on microbial TCE isotope fractionation including adaptation period to TCE exposure, temperature, electron donor/acceptor concentration, and supplied cobalt species, as well as coculture effects. Desulfitobacterium hafniense strain Y51 was chosen as a model organism, as it contains only one reductive dehalogenase enzyme allowing for an unequivocal assignment of observed isotope fractionation variability to specific environmental factors. In 20 independent TCE transformation experiments, the ϵCvalues differed only slightly by 1‰ despite drastic variations in the growth conditions. These robust ϵCvalues reflect the intrinsic isotope fractionation of the TCE-catalyzing enzyme, as changes in both, the enzymatic reaction mechanism and rate-determining steps, can be excluded based on robust two-dimensional isotope analysis (δ »13C/δ »37Cl). Thus, growth conditions that cells, holding only one enzyme for TCE transformation, encounter in the environment are not expected to affect isotope fractionation during biotransformation and thus likely do not contribute to the reported variability of carbon and chlorine isotope enrichment factors for reductive dechlorination of TCE.

Original languageEnglish (US)
Pages (from-to)2510-2518
Number of pages9
JournalACS Environmental Science and Technology Water
Volume2
Issue number12
DOIs
StatePublished - Dec 9 2022

Bibliographical note

Funding Information:
The authors thank Sharmishtha Jindal, Stefan Engelhart, and Charlotte Schmidt for laboratory assistance. D. hafniense strain Y51 was kindly provided by Prof. Furukawa in the Department of Bioscience and Biotechnology at Kyushu University (Japan). Financial support was provided by the German Research Foundation (grant HA3453/12-1). Financial support was provided by the German Research Foundation (grant HA3453/12-1).

Publisher Copyright:
© The Author(s) 2022.

Keywords

  • Desulfitobacterium hafniense strain Y51
  • chlorinated ethenes
  • compound-specific isotope analysis
  • dual-isotope analysis
  • groundwater contaminants
  • organohalide-respiring bacteria
  • reductive dechlorination
  • reductive dehalogenases

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