Sandra Dworatzek and Jennifer Webb are Coauthors on a Research Paper which Sheds Light on Carbon and Chlorine Isotope Fractionation during Reductive Dechlorination

Sandra Dworatzek, M.Sc. and Jennifer Webb, M.Sc. coauthored a paper entitled “Investigation of active site amino acid influence on carbon and chlorine isotope fractionation during reductive dechlorination” that was published in the FEMS Microbiology Ecology journal in Volume 98, Issue 8 in August 2022.

Sandra and Jennifer’s coauthors include Elizabeth Phillips, Olivia Bulka, Katherine Picott, Steffen Kümmel, Elizabeth A Edwards, Ivonne Nijenhuis, Matthias Gehre, and Barbara Sherwood Lollar.

Sandra is a Principal Scientist with more than 25 years of experience in bioremediation of chlorinated solvents, petroleum hydrocarbons, emerging contaminants and other recalcitrant compounds.

Jennifer is the Research Coordinator at SiREM with more than 17 years of experience in microbiology where she develops new cultures while coordinating R&D collaborations with researchers globally.

FEMS Microbiology Ecology publishes high quality papers that make a significant contribution to the field. It covers microorgansims in soil, aqautic, and atmospheric habitats – including extreme environments – and includes natural, artificial and managed systems.


Reductive dehalogenases (RDases) are corrinoid-dependent enzymes that reductively dehalogenate organohalides in respiratory processes. By comparing isotope effects in biotically catalyzed reactions to reference experiments with abiotic corrinoid catalysts, compound-specific isotope analysis (CSIA) has been shown to yield valuable insights into enzyme mechanisms and kinetics, including RDases. Here, we report isotopic fractionation (ε) during biotransformation of chloroform (CF) for carbon (εC = -1.52 ± 0.34‰) and chlorine (εCl = -1.84 ± 0.19‰), corresponding to a ΛC/Cl value of 1.13 ± 0.35. These results are highly suppressed compared to isotope effects observed both during CF biotransformation by another organism with a highly similar RDase (>95% sequence identity) at the amino acid level, and to those observed during abiotic dehalogenation of CF. Amino acid differences occur at four locations within the two different RDases’ active sites, and this study examines whether these differences potentially affect the observed εC, εCl, and ΛC/Cl. Structural protein models approximating the locations of the residues elucidate possible controls on reaction mechanisms and/or substrate binding efficiency. These four locations are not conserved among other chloroalkane reducing RDases with high amino acid similarity (>90%), suggesting that these locations may be important in determining isotope fractionation within this homologous group of RDases.

More Information

Read the article: Investigation of active site amino acid influence on carbon and chlorine isotope fractionation during reductive dechlorination

Learn more about the journal: FEMS Microbiology Ecology

Learn more about Sandra Dworatzek at: Sandra Dworatzek | LinkedIn

Learn more about Jennifer Webb at: Jennifer Webb | LinkedIn