Isolation and Characterization of Dehalococcoides Sp. Strain FL2, a Trichloroethene (TCE)- And 1,2-dichloroethene-respiring Anaerobe

Environ Microbiol. 2005 Sep;7(9):1442-50. doi: 10.1111/j.1462-2920.2005.00830.x.

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Bacteria, Anaerobic / genetics
  • Bacteria, Anaerobic / growth & development
  • Bacteria, Anaerobic / isolation & purification*
  • Biodegradation, Environmental
  • Dichloroethylenes / analysis*
  • Fresh Water / microbiology*
  • Genes, Bacterial
  • Geologic Sediments / microbiology*
  • Phylogeny
  • RNA, Bacterial / genetics
  • RNA, Ribosomal, 16S / genetics
  • Trichloroethylene / analysis*
  • Water Pollutants, Chemical / analysis*

Substances

  • Dichloroethylenes
  • RNA, Bacterial
  • RNA, Ribosomal, 16S
  • Water Pollutants, Chemical
  • Trichloroethylene
  • 1,2-dichloroethylene