title: Characterization of a Dehalobacter coculture that dechlorinates 1,2-dichloroethane to ethene and identification of the putative reductive dehalogenase gene.
abstract: Dehalobacter and "Dehalococcoides" spp. were previously shown to be involved in the biotransformation of 1,1,2-trichloroethane (1,1,2-TCA) and 1,2-dichloroethane (1,2-DCA) to ethene in a mixed anaerobic enrichment culture. Here we report the further enrichment and characterization of a Dehalobacter sp. from this mixed culture in coculture with an Acetobacterium sp. Through a series of serial transfers and dilutions with acetate, H(2), and 1,2-DCA, a stable coculture of Acetobacterium and Dehalobacter spp. was obtained, where Dehalobacter grew during dechlorination. The isolated Acetobacterium strain did not dechlorinate 1,2-DCA. Quantitative PCR with specific primers showed that Dehalobacter cells did not grow in the absence of a chlorinated electron acceptor and that the growth yield with 1,2-DCA was 6.9 (+/-0.7) x 10(7) 16S rRNA gene copies/mumol 1,2-DCA degraded. PCR with degenerate primers targeting reductive dehalogenase genes detected three distinct Dehalobacter/Desulfitobacterium-type sequences in the mixed-parent culture, but only one of these was present in the 1,2-DCA-H(2) coculture. Reverse transcriptase PCR revealed the transcription of this dehalogenase gene specifically during the dechlorination of 1,2-DCA. The 1,2-DCA-H(2) coculture could dechlorinate 1,2-DCA but not 1,1,2-TCA, nor could it dechlorinate chlorinated ethenes. As a collective, the genus Dehalobacter has been show to dechlorinate many diverse compounds, but individual species seem to each have a narrow substrate range.
authors.affiliation: Department of Botany, University of Toronto, Toronto, ON M5S 3E5, Canada.
authors.forename: Ariel
authors.initials: A
authors.lastname: Grostern
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Edwards
mesh_terms: D045855:Acetobacterium / Q000254:growth & development / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D018920:Coculture Techniques; D015169:Colony Count, Microbial / Q000379:methods; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005025:Ethylene Dichlorides / Q000378:metabolism*; D005030:Ethylenes / Q000378:metabolism*; D006867:Hydrolases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010459:Peptococcaceae / Q000254:growth & development / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D014240:Trichloroethanes / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D005025:Ethylene Dichlorides; D005030:Ethylenes; D014240:Trichloroethanes; C024567:1,1,2-trichloroethane; C024565:ethylene dichloride; C036216:ethylene; D006867:Hydrolases