Trichloromethane dechlorination by a novel Dehalobacter sp. strain 8M reveals a third contrasting C and Cl isotope fractionation pattern within this genus

Jesica M. Soder-Walz, Clara Torrentó, Camelia Algora, Kenneth Wasmund, Pilar Cortés, Albert Soler, Teresa Vicent, Mònica Rosell*, Ernest Marco-Urrea

*Corresponding author for this work

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Abstract

Trichloromethane (TCM) is a pollutant frequently detected in contaminated aquifers, and only four bacterial strains are known to respire it. Here, we obtained a novel Dehalobacter strain capable of transforming TCM to dichloromethane, which was denominated Dehalobacter sp. strain 8M. Besides TCM, strain 8M also completely transformed 1,1,2-trichloroethane to vinyl chloride and 1,2-dichloroethane. Quantitative PCR analysis for the 16S rRNA genes confirmed growth of Dehalobacter with TCM and 1,1,2-trichloroethane as electron acceptors. Carbon and chlorine isotope fractionation during TCM transformation was studied in cultured cells and in enzymatic assays with cell suspensions and crude protein extracts. TCM transformation in the three studied systems resulted in small but significant carbon (εC = −2.7 ± 0.1‰ for respiring cells, −3.1 ± 0.1‰ for cell suspensions, and − 4.1 ± 0.5‰ for crude protein extracts) and chlorine (εCl = −0.9 ± 0.1‰, −1.1 ± 0.1‰, and − 1.2 ± 0.2‰, respectively) isotope fractionation. A characteristic and consistent dual C[sbnd]Cl isotope fractionation pattern was observed for the three systems (combined ΛC/Cl = 2.8 ± 0.3). This ΛC/Cl differed significantly from previously reported values for anaerobic dechlorination of TCM by the corrinoid cofactor vitamin B12 and other Dehalobacter strains. These findings widen our knowledge on the existence of different enzyme binding mechanisms underlying TCM-dechlorination within the genus Dehalobacter and demonstrates that dual isotope analysis could be a feasible tool to differentiate TCM degraders at field studies.

Original languageEnglish
Article number152659
Number of pages9
JournalScience of the Total Environment
Volume813
Early online date24 Dec 2021
DOIs
Publication statusPublished - 20 Mar 2022

Keywords

  • 1,1,2-trichloroethane
  • 2D-CSIA
  • Dehalobacter
  • Isotopic fractionation
  • Organohalide respiration
  • Trichloromethane

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