Distinct Dual C-Cl Isotope Fractionation Patterns during Anaerobic Biodegradation of 1,2-Dichloroethane: Potential to Characterize Microbial Degradation in the Field
This study investigates, for the first time, dual C-Cl isotope fractionation during anaerobic biodegradation of 1,2-dichloroethane (1,2-DCA) via dihaloelimination by Dehalococcoides and Dehalogenimonas-containing enrichment cultures. Isotopic fractionation of 1,2-DCA (εbulkC and εbulkCl) for Dehalococcoides (-33.0 ± 0.4‰ and -5.1 ± 0.1‰) and Dehalogenimonas-containing microcosms (-23 ± 2‰ and -12.0 ± 0.8‰) resulted in distinctly different dual element C-Cl isotope correlations (∇ = Δδ13C/Δδ37Cl ≈ εbulkC/εbulkCl), 6.8 ± 0.2 and 1.89 ± 0.02, respectively. Determined isotope effects and detected products suggest that the difference on the obtained ∇ values for biodihaloelimination could be associated with a different mode of concerted bond cleavage rather than two different reaction pathways (i.e., stepwise vs concerted). ∇ values of 1,2-DCA were, for the first time, determined in two field sites under reducing conditions (2.1 ± 0.1 and 2.2 ± 2.9). They were similar to the one obtained for the Dehalogenimonas-containing microcosms (1.89 ± 0.02) and very different from those reported for aerobic degradation pathways in a previous laboratory study (7.6 ± 0.1 and 0.78 ± 0.03). Thus, this study illustrates the potential of a dual isotope analysis to differentiate between aerobic and anaerobic biodegradation pathways of 1,2-DCA in the field and suggests that this approach might also be used to characterize dihaloelimination of 1,2-DCA by different bacteria, which needs to be confirmed in future studies. © 2017 American Chemical Society. ; We thoroughly thank four anonymous reviewers for their helpful comments on the manuscript. J.P. was supported by the University of Neuchatel via direct university funding. E.M-U is ̂ supported by the Spanish Ministry of Economy and Competitiveness and FEDER (project CTM2013-48545-C2- 1-R) and the Xarxa de Referencia en Biotecnologia de la ̀ Generalitat de Catalunya. MAG group is supported by Spanish Government REMEDIATION project (CGL2014-57215-C4-1- R) and the Catalan Government project 2014SGR-1456. S.H.M acknowledges support from the Ministry of Education Malaysia (SLAI-UMP Scholarship) for a predoctoral fellowship and M.R. a Ramon y Cajal contract (RYC-2012-11920). ; Peer reviewed