Dehalococcoides

In taxonomy, the Dehalococcoides are a genus of the Dehalococcoidetes.

Dehalococcoides obtain energy from reductive dehalogenation of halogenated organic compounds. Halogenated organics are the electron acceptor and hydrogen gas is the only known electron donor. It is enhanced used during bioremediation of PCE and TCE contaminated ground water sites either by adding fermentable substrate to create hydrogen gas or by directly adding a mixed culture containing Dehalococcoides. KB-1 is one commercially available product from Geosyntec to environmental engineers interested in bioaugmentation of PCE and TCE contaminated sites. 

Dehalococcoides ethenogenes strain 195 was first grown in pure culture at Cornell University by Xavier Maymó-Gatell ''et. al.'' and published in 1997. Since then there have been many other phylogenitically similar organisms. Work is continuing at Cornell University investigating this organisms properties and its role in bioremediation. []

Its population in groundwater is critical to encouraging the bioremediation of dense-non-aqueous-phase-liquids (DNAPL) contaminated sites. Groundwater remediation processes are often stalled if the population of dehalococcoides is not sufficient enough or there is no electron donor. There are other dechlorinating microbes that are also responsible for degrading tetrachloroethane (PCE) to trichloroethane (TCE) to 1,2-Dichloroethene (1,2-DCE). Unfortunately, these other microbes often fail to continue the degradation process onward to vinyl chloride (VC), and finally to ethene. Since this is the process that dehalococcoides is responsible for (1,2-DCE to VC to Ethene), its presence in the groundwater of a DNAPL contaminated site is imperative to properly bioremediate the site.

There are many complexities to the environmental remediation of DNAPL contaminated sites. There are processes that are often used while remediating a site beyond biodegredation, which can include biostimulation and bioaugmentation. Additionally, it should be known that there are other non-biological remediation options that exist too, and are usually explored on a site by site basis to determine the most effective solution for each specific site. One recent use of dehalococcoides includes the remediation of potential PCB dredge sites. 

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