Dehalococcoides
| Dehalococcoides | |
|---|---|
| Scientific classification | |
| Domain: | Bacteria |
| Phylum: | Chloroflexi |
| Class: | Dehalococcoidia |
| Genus: | Dehalococcoides Maymo-Gatell et al. 1997 |
| Species | |
Dehalococcoides is a genus of bacteria within class Dehalococcoidia that obtain energy via the oxidation of hydrogen and subsequent reductive dehalogenation of halogenated organic compounds in a mode of anaerobic respiration called organohalide respiration. They are well known for their great potential to remediate halogenated ethenes and aromatics. They are the only bacteria known to transform highly chlorinated dioxins, PCBs. In addition, they are the only known bacteria to transform tetrachloroethene (perchloroethene, PCE) to ethene.
The first member of the genus Dehalococcoides was described in 1997 as Dehalococcoides ethenogenes strain 195. Additional Dehalococcoides members were later described as strains CBDB1, BAV1, FL2, VS, and GT. In 2012 all yet-isolated Dehalococcoides strains were summarized under the new taxonomic name D. mccartyi.
Dehalococcoides are obligately organohalide-respiring bacteria, which means that they can only grow by using halogenated compounds as electron acceptor. They use hydrogen as an electron donor. Energy is generated by transferring electrons from hydrogen to the halogenated electron acceptor. To synthesize cell material Dehalococcoides strains additionally need actate.
Dehalococcoides can transform many highly toxic and/or persistent compounds that are not transformed by any other known bacteria. This included tetrachloroethene (PCE) and trichloroethene (TCE) which is transformed to the non-toxic ethene, chlorinated dioxins, benzenes, PCBs, phenols and many other aromatic substrates.
By transforming all these halogenated compounds they are seen as an important helper to treat contaminated ground water sites. Their capacity to grow by using the contaminants as energy source allows them to distribute in a contaminated soil or groundwater and offers great promises for the in situ use. Several companies worldwide now use Dehalococcoides-containing mixed cultures for commercial remediation efforts.
The presence of bacteria of the genus Dehalococcoides is a prerequisite to induce complete detoxification of halogenated ethenes (often described as dense non-aqueous phase liquids (DNAPL)) to the non-toxic ethene. For treatment of contaminated sites apart from an active culture also electron acceptors have to be added. Most often, these are oxidizable substrates (e.g. lactate) to form hydrogen in situ.
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