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| Dehalococcoides | |
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| Genus: | Dehalococcoides
Maymo-Gatell et al. 1997 |
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Dehalococcoides is a genus of bacteria within the class Dehalococcoidetes that conserve metabolic energy by coupling the oxidation of hydrogen gas (H2) with the reduction of halogenated organic compounds through a process known as reductive dehalogenation.[1] It should be noted that a formal description of the candidate genus Dehalococcoides has not been published in the taxonomic literature to date, and that Dehalococcoides is currently absent from the List of Bacterial names with Standing in Nomenclature. The first Dehalococcoides enrichment was performed in the year 1995 (REF), and the first isolate, Dehalococcoides ethenogenes strain 195, was described in 1997 (REF). Strain 195 gained notoriety as the first known organism capable of complete reduction of the dry-cleaning solvent, tetrachloroethene, also referred to as PCE [2][3]. This finding is especially important to the field of bioremediation and environmental protection because PCE and other chloroethenes comprise the most common groundwater contaminants in the United States of America ((REF)). They are similarly ubiquitous throughout the developed world ((REF)). The complete reduction of PCE to ethene by Dehalococcoides occurs in a step-wise manner.
Although there are other dechlorinating microbesresponsible for the environmental catalysis of PCE → TCE → 1,2-Dichloroethene (1,2-DCE), only Dehalococcoides are known to continue the degradation sequence from 1,2-DCE to vinyl chloride (VC), and finally, ethene (1,2-DCE → VC → ethene), which is environmentally benign. The presence of Dehalococcoides in groundwater may be necessary for proper bioremediation of contaminated sites. In addition to chloroethenes, members of Dehalococcoides are now known to be capable of the reductive dehalogenation of other priority pollutants, including polychlorinated biphenyls, dioxins, chlorobenzenes, chlorophenols, chloroethanes, etc. ((REFs))
Taxonomy / Phylogeny
Other strains of Dehalococcoides have since been identified and isolated, each having varying capabilities for the dechlorination of halogenated organic comounds. The following is a list of Dehalococcoides strains and enrichment cultures described in the primary scientific literature, in order of first description.
strain 195
strain CBDB1
strain BAV1
strain VS
strain FL2
culture KB-1
culture ANAS
Reductive Dehalogenation
What is known about the process of reductive dehalogenation in Dehalococcoides to date.
Magnuson, J K (April 1998). "Reductive dechlorination of tetrachloroethene to ethene by a two-component enzyme pathway". Appl Environ Microbiol. 64 (4): 1270–5. doi:10.1128/AEM.64.4.1270-1275.1998. PMC 106140. PMID 10671186. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
Bioremediation
High Dehalococcoides population numbers and electron substrate concentrations are necessary for effective bioremediation of dense non-aqueous phase liquids (DNAPL) at contaminated sites. Addition of either fermentable organic compounds (e.g. lactate or propionate) to create H2 in situ, is typically required. Often contaminated sites lack a native population of Dehalococcoides that can effectively remediate the contaminants, in which case bioaugmentation of the site with a mixed culture containing specific Dehalococcoides strains is required.
Nutritional Requirements
A comparison of media uses and a list of known or suspected nutritional requirements.
References
- ^ See the NCBI webpage on Dehalococcoides. Data extracted from the "NCBI taxonomy resources". National Center for Biotechnology Information. Retrieved 2007-03-19.
- ^ Maymo-Gatell X, Chien Y, Gossett JM, Zinder SH (1997). "Isolation of a bacterium that reductively dechlorinates tetrachloroethene to ethene". Science. 276 (5318): 1568–1571. doi:10.1126/science.276.5318.1568. PMID 9171062.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Steele, Bill (2007-06-14). "Computer modeling could help chlorine-hungry bacteria break down toxic waste". Chronicle Online. Cornell University. Retrieved 2007-11-24.
