Complete Detoxification of Short Chain Chlorinated Aliphatic Compounds: Isolation of Halorespiring Organisms and Biochemical Studies of the Dehalogenating Enzyme Systems - Final Report Page: 3 of 21
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1. Executive Summary
The stimulation of halorespiring microorganisms is potentially the most promising and cost-
effective technology for remediating sites contaminated with chlorinated solvents. Central to the
successful implementation of such a bioremediation technology is the determination of the presence
of halorespiring organisms and information on their physiology. Unfortunately, our knowledge of
halorespiring microbes that detoxify chlorinated solvents is limited. Hence, our work focused on
the isolation and characterization of halorespiring populations, and the initial investigation of the
dechlorinating enzyme systems. In addition, tools to evaluate the presence/activity of halorespiring
populations in the environment were developed.
Halorespiring enrichment cultures were obtained from a variety of contaminated and non-
contaminated sites. Five enrichments completely dechlorinated tetrachloroethene (PCE) to ethene,
and four different cultures dechlorinated 1,2-dichloropropane to propene. Hydrogen consumption
threshold measurements and the determination of the fraction of electrons going towards reductive
dechlorination confirmed the presence of halorespirers. Two halorespiring isolates were obtained:
Desulfuromonas ottawaensis strain BB 1, which dechlorinates PCE to cis-1,2-dichloroethene, and
Desulfitobacterium sp. strain Vietl, which dechlorinates PCE to trichloroethene. Desulfuromonas
ottawaensis strain BB 1 dechlorinated PCE at rates of 150 nmol min- mg of protein1 with acetate as
the electron donor. In cell-free systems PCE was dechlorinated at rates of at least 300 nmol min-'
mg of protein-1 with methyl viologen as the electron donor. In addition, a defined mixed culture
consisting of three populations including a Dehalococcoides species was obtained. This mixed
culture completely dechlorinated PCE to the environmentally benign product ethene.
Specific primers based on 16S rDNA sequences of Desulfuromonas ottawaensis strain BB 1
and the Dehalococcoides species were designed, and used in a nested PCR approach for the
sensitive and specific detection of these organisms in environmental samples. Both dechlorinators
were detected in three out of three river sediment samples tested, and two different contaminated
aquifers tested positive with the Desulfuromonas ottawaensis- and Dehaloccocoides-targeted
primers, respectively.
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Tiedje, J.M. Complete Detoxification of Short Chain Chlorinated Aliphatic Compounds: Isolation of Halorespiring Organisms and Biochemical Studies of the Dehalogenating Enzyme Systems - Final Report, report, October 1, 1999; United States. (https://digital.library.unt.edu/ark:/67531/metadc720642/m1/3/: accessed April 20, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.