title: Quantifying the effects of 1,1,1-trichloroethane and 1,1-dichloroethane on chlorinated ethene reductive dehalogenases.
abstract: Mixtures of chlorinated ethenes and ethanes are often found at contaminated sites. In this study, we undertook a systematic investigation of the inhibitory effects of 1,1,1-trichloroethane (1,1,1-TCA) and 1,1-dichloroethane (1,1-DCA) on chlorinated ethene dechlorination in three distinct Dehalococcoides-containing consortia. To focus on inhibition acting directly on the reductive dehalogenases, dechlorination assays used cell-free extracts prepared from cultures actively dechlorinating trichloroethene (TCE) to ethene. The dechlorination assays were initiated with TCE, cis-1,2-dichloroethene (cDCE), or vinyl chloride (VC) as substrates and either 1,1,1-TCA or 1,1-DCA as potential inhibitors. 1,1,1-TCA inhibited VC dechlorination similarly in cell suspension and cell-free extract assays, implicating an effect on the VC reductases associated with the dechlorination of VC to nontoxic ethene. Concentrations of 1,1,1-TCA in the range of 30-270 μg/L reduced VC dechlorination rates by approximately 50% relative to conditions without 1,1,1-TCA. 1,1,1-TCA also inhibited reductive dehalogenases involved in TCE and cDCE dechlorination. In contrast, 1,1-DCA had no pronounced inhibitory effects on chlorinated ethene reductive dehalogenases, indicating that removal of 1,1,1-TCA via reductive dechlorination to 1,1-DCA is a viable strategy to relieve inhibition.
authors.affiliation: Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, ON, Canada M5S 3E5.
authors.forename: Winnie W M
authors.initials: WW
authors.lastname: Chan
authors.forename: Ariel
authors.initials: A
authors.lastname: Grostern
authors.forename: Frank E
authors.initials: FE
authors.lastname: Löffler
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Edwards
mesh_terms: D001673:Biodegradation, Environmental; D041862:Chloroflexi / Q000201:enzymology*; D005018:Ethyl Chloride / Q000031:analogs & derivatives* / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism*; D054879:Halogenation; D007700:Kinetics; D010084:Oxidation-Reduction; D014240:Trichloroethanes / Q000378:metabolism*
chemical_list: D005030:Ethylenes; D014240:Trichloroethanes; C501196:1,1-dichloroethane; C024566:1,1,1-trichloroethane; D005018:Ethyl Chloride; C036216:ethylene