title: Isolation and characterization of Dehalococcoides sp. strain FL2, a trichloroethene (TCE)- and 1,2-dichloroethene-respiring anaerobe.
abstract: A strictly anaerobic bacterium was isolated from tetrachloroethene (PCE)-to-ethene dechlorinating microcosms established with river sediment without prior exposure to chlorinated solvents. The isolation procedure included the addition of 2-bromoethanesulfonate to select against methanogenic archaea, >50 consecutive 1-2% (v/v) transfers to reduced mineral salts medium amended with trichloroethene (TCE), acetate, and hydrogen, the addition of ampicillin, and the dilution-to-extinction principle. Culture-dependent and 16S rRNA gene-targeted approaches suggested culture purity. Microscopic examination revealed a homogeneous culture of an organism with a distinct, disc-shaped morphology. The isolate shared >99% 16S rRNA gene sequence similarity with members of the Pinellas group of the Dehalococcoides cluster, and was designated Dehalococcoides sp. strain FL2. Strain FL2 could be propagated with TCE, cis-1,2-dichloroethene (cis-DCE), or trans-DCE as the electron acceptors, acetate as the carbon source, and hydrogen as the electron donor in defined, completely synthetic medium. No other growth-supporting redox couples were identified. Trichloroethene, cis-DCE and trans-DCE were dechlorinated at rates of 27.5, 30.4 and 18.8 micromol l-1 day-1 respectively. Quantitative real-time polymerase chain reaction (PCR) with a fluorescently labelled linear hybridization probe confirmed growth with these electron acceptors, and suggested that strain FL2 captures energy from both the TCE-to-cis-DCE and 1,2-DCE-to-VC dechlorination steps. Tetrachloroethene and vinyl chloride (VC) were slowly and cometabolically dechlorinated in the presence of a growth-supporting chloroethene, but ethene formation was incomplete, even after prolonged incubation. At room temperature, strain FL2 grew with a doubling time of 2.4 days, and yielded 166.1+/-10.2 mg of protein per mole of chloride released. In the presence of excess electron acceptor, strain FL2 consumed hydrogen to a concentration of 0.061+/-0.016 nM. Dechlorination ceased following the addition of 0.5 mM sulfite, whereas sulfate (10 mM) and nitrate (5 mM) had no inhibitory effects.
authors.affiliation: School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA.
authors.forename: Jianzhong
authors.initials: J
authors.lastname: He
authors.forename: Youlboong
authors.initials: Y
authors.lastname: Sung
authors.forename: Rosa
authors.initials: R
authors.lastname: Krajmalnik-Brown
authors.forename: Kirsti M
authors.initials: KM
authors.lastname: Ritalahti
authors.forename: Frank E
authors.initials: FE
authors.lastname: Löffler
mesh_terms: D001421:Bacteria, Anaerobic / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D001673:Biodegradation, Environmental; D004000:Dichloroethylenes / Q000032:analysis*; D005618:Fresh Water / Q000382:microbiology*; D005798:Genes, Bacterial; D019015:Geologic Sediments / Q000382:microbiology*; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D014241:Trichloroethylene / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D004000:Dichloroethylenes; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D014874:Water Pollutants, Chemical; D014241:Trichloroethylene; C035384:1,2-dichloroethylene