Lihl, C. ; Douglas, L.M.* ; Franke, S.* ; Pérez-de-Mora, A. ; Meyer, A.H. ; Daubmeier, M. ; Edwards, E.A.* ; Nijenhuis, I.* ; Sherwood Lollar, B.* ; Elsner, M.
Mechanistic dichotomy in bacterial trichloroethene dechlorination revealed by carbon and chlorine isotope effects.
Environ. Sci. Technol. 53, 4245-4254 (2019)
Tetrachloroethene (PCE) and trichloroethene (TCE) are significant groundwater contaminants. Microbial reductive dehalogenation at contaminated sites can produce nontoxic ethene but often stops at toxic cis-1,2-dichloroethene (cis-DCE) or vinyl chloride (VC). The magnitude of carbon relative to chlorine isotope effects (as expressed by Lambda(C/Cl), the slope of delta C-13 versus delta Cl-37 regressions) was recently recognized to reveal different reduction mechanisms with vitamin B-12 as a model reactant for reductive dehalogenase activity. Large Lambda(C/Cl) values for cis-DCE reflected cob(I)alamin addition followed by protonation, whereas smaller Lambda(C/Cl) values for PCE evidenced cob(I)alamin addition followed by Cl- elimination. This study addressed dehalogenation in actual microorganisms and observed identical large Lambda(C/Cl) values for cis-DCE (Lambda(C/Cl) = 10.0 to 17.8) that contrasted with identical smaller Lambda(C/Cl) for TCE and PCE (Lambda(C/Cl) = 2.3 to 3.8). For TCE, the trend of small Lambda(C/Cl) could even be reversed when mixed cultures were precultivated on VC or DCEs and subsequently confronted with TCE (Lambda(C/Cl) = 9.0 to 18.2). This observation provides explicit evidence that substrate adaptation must have selected for reductive dehalogenases with different mechanistic motifs. The patterns of Lambda(C/Cl) are consistent with practically all studies published to date, while the difference in reaction mechanisms offers a potential answer to the long-standing question of why bioremediation frequently stalls at cis-DCE.
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Publication type
Article: Journal article
Document type
Scientific Article
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Keywords
Ratio Mass-spectrometry; Reductive Dechlorination; Dehalococcoides-ethenogenes; Vinyl-chloride; Microbial-degradation; Organic Contaminants; Fractionation; Tetrachloroethene; Ethene; Transformation
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Language
english
Publication Year
2019
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2019
ISSN (print) / ISBN
0013-936X
e-ISSN
1520-5851
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Volume: 53,
Issue: 8,
Pages: 4245-4254
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ACS
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Washington, DC
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Reviewing status
Peer reviewed
POF-Topic(s)
20403 - Sustainable Water Management
Research field(s)
Environmental Sciences
PSP Element(s)
G-504390-001
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Erfassungsdatum
2019-05-08