Dehalococcoides is a genus of bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 within class Dehalococcoidetes

Dehalococcoidetes

"Dehalococcoides" is a class of "Chloroflexi", a phylum of Bacteria. It is also known as the DHC group.The name "Dehalococcoidetes" is a placeholder name given by Hugenholtz and Stackebrandt, 2004, after "Dehalococcoides ethenogenes" a partially described species in 1997, whereas the first species...

 that obtain energy via the oxidation of hydrogen gas and subsequent reductive dehalogenation

Reductive dechlorination

Reductive dechlorination is a term that is used to describe certain types of degradation of chlorinated organic compounds by chemical reduction with release of inorganic chloride ions.- Biological :...

 of halogenated organic compounds.

Reductive dehalogenation

The first member of the "Dehalococcoides" (DHC) group, "Dehalococcoides ethenogenes" strain 195 (DET) was described in 1997, and is noted for its potential use in the bioremediation of tetrachloroethene (PCE) and trichloroethene (TCE) contaminated ground water sites. Additional DHC members were later described. These include CBDB1 , BAV1, VS, and GT. High DHC population numbers and electron substrate concentrations are necessary for effective bioremediation of dense non-aqueous phase liquids (DNAPL) contamination sites. Addition of either fermentable substrate to create hydrogen gas in situ, or inoculation of the site with mixed cultures containing Dehalococcoides are required for effective remediation.

Other dechlorinating microbes are also responsible for the PCE → TCE → 1,2-Dichloroethene

1,2-Dichloroethene

1,2-Dichloroethene, commonly called 1,2-dichloroethylene or 1,2-DCE, is an organochloride with the molecular formula C2H2Cl2. It is a highly flammable, colorless liquid with a sharp, harsh odor. It can exist as either of two geometric isomers, cis-1,2-dichloroethene or trans-1,2-dichloroethene,...

 (1,2-DCE) sequence of ethene dehalogenation, but these organisms often fail to continue the degradation sequence from 1,2-DCE to vinyl chloride

Vinyl chloride

Vinyl chloride is the organochloride with the formula H2C:CHCl. It is also called vinyl chloride monomer, VCM or chloroethene. This colorless compound is an important industrial chemical chiefly used to produce the polymer polyvinyl chloride . At ambient pressure and temperature, vinyl chloride...

 (VC), and finally, ethene (1,2-DCE → VC → ethene), which is environmentally benign. Dehalococcoides effectively converts 1,2-DCE to VC, and its presence in groundwater may be necessary for proper bioremediation of contaminated sites.

Mixed Dehalococcoides species can also bioremediate environmental sites contaminated with polychlorinated biphenyls (PCBs).