title: Detoxification of 1,1,2-trichloroethane to ethene by desulfitobacterium and identification of its functional reductase gene.
abstract: 1,1,2-trichloroethane (1,1,2-TCA) has become a common groundwater pollutant due to historically extensive utilization, improper disposal, as well as from incomplete dechlorination of 1,1,2,2-tetrachloroethane. Currently, limited information is available on microbial detoxification of 1,1,2-TCA. Desulfitobacterium sp. strain PR, which was isolated from an anaerobic bioreactor maintained to dechlorinate chloroethenes/ethanes, exhibited the capacity to dechlorinate 1,1,1-trichloroethane and chloroform. In this study, the dechlorinating ability of strain PR was further explored. Strain PR showed the capability to dechlorinate 1,1,2-TCA (~1.12 mM) predominantly to 1,2-dichloroethane (1,2-DCA) and chloroethane, and to trace amounts of vinyl chloride and ethene within 20 days. Strain PR coupled growth with dechlorination of 1,1,2-TCA to 1,2-DCA, while no cell growth was observed with dechlorination of 1,2-DCA to chloroethane. Later, through transcriptomic and enzymatic analysis, the reductive dehalogenase CtrA, which was previously reported to be responsible for 1,1,1-trichloroethane and chloroform dechlorination, was identified as the 1,1,2-TCA reductive dehalogenase. Since trichloroethene (TCE) is usually co-contaminated with 1,1,2-TCA, a co-culture containing Dehalococcoides mccartyi strain 11a capable of detoxifying TCE and 1,2-DCA and strain PR was established. Interestingly, this co-culture dechlorinated 1,1,2-TCA and TCE to the non-toxic end-product ethene within 48 days without chloroethane production. This novel pathway avoids production of the carcinogenic intermediate dechlorination product vinyl chloride, providing a more environmentally friendly strategy to treat 1,1,2-TCA.
authors.affiliation: Department of Civil and Environmental Engineering, National University of Singapore, Singapore, 117576, Singapore.
authors.forename: Siyan
authors.initials: S
authors.lastname: Zhao
authors.affiliation: Department of Civil and Environmental Engineering, National University of Singapore, Singapore, 117576, Singapore.
authors.forename: Chang
authors.initials: C
authors.lastname: Ding
authors.affiliation: Department of Civil and Environmental Engineering, National University of Singapore, Singapore, 117576, Singapore.
authors.forename: Jianzhong
authors.initials: J
authors.lastname: He
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001673:Biodegradation, Environmental; D001711:Biotransformation; D045858:Desulfitobacterium / Q000235:genetics* / Q000378:metabolism*; D005030:Ethylenes / Q000378:metabolism*; D014240:Trichloroethanes / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D005030:Ethylenes; D014240:Trichloroethanes; C024567:1,1,2-trichloroethane; C036216:ethylene
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