TY - JOUR
T1 - Mechanistic Dichotomy in Bacterial Trichloroethene Dechlorination Revealed by Carbon and Chlorine Isotope Effects
AU - Lihl, Christina
AU - Douglas, Lisa M.
AU - Franke, Steffi
AU - Pérez-De-Mora, Alfredo
AU - Meyer, Armin H.
AU - Daubmeier, Martina
AU - Edwards, Elizabeth A.
AU - Nijenhuis, Ivonne
AU - Sherwood Lollar, Barbara
AU - Elsner, Martin
N1 - Publisher Copyright:
© Copyright 2019 American Chemical Society.
PY - 2019/4/16
Y1 - 2019/4/16
N2 - 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 IC/Cl, the slope of Î13C versus Î37Cl regressions) was recently recognized to reveal different reduction mechanisms with vitamin B12 as a model reactant for reductive dehalogenase activity. Large IC/Cl values for cis-DCE reflected cob(I)alamin addition followed by protonation, whereas smaller IC/Cl values for PCE evidenced cob(I)alamin addition followed by Cl- elimination. This study addressed dehalogenation in actual microorganisms and observed identical large IC/Cl values for cis-DCE (IC/Cl = 10.0 to 17.8) that contrasted with identical smaller IC/Cl for TCE and PCE (IC/Cl = 2.3 to 3.8). For TCE, the trend of small IC/Cl could even be reversed when mixed cultures were precultivated on VC or DCEs and subsequently confronted with TCE (IC/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 IC/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.
AB - 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 IC/Cl, the slope of Î13C versus Î37Cl regressions) was recently recognized to reveal different reduction mechanisms with vitamin B12 as a model reactant for reductive dehalogenase activity. Large IC/Cl values for cis-DCE reflected cob(I)alamin addition followed by protonation, whereas smaller IC/Cl values for PCE evidenced cob(I)alamin addition followed by Cl- elimination. This study addressed dehalogenation in actual microorganisms and observed identical large IC/Cl values for cis-DCE (IC/Cl = 10.0 to 17.8) that contrasted with identical smaller IC/Cl for TCE and PCE (IC/Cl = 2.3 to 3.8). For TCE, the trend of small IC/Cl could even be reversed when mixed cultures were precultivated on VC or DCEs and subsequently confronted with TCE (IC/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 IC/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.
UR - http://www.scopus.com/inward/record.url?scp=85064536456&partnerID=8YFLogxK
U2 - 10.1021/acs.est.8b06643
DO - 10.1021/acs.est.8b06643
M3 - Article
C2 - 30857389
AN - SCOPUS:85064536456
SN - 0013-936X
VL - 53
SP - 4245
EP - 4254
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 8
ER -