Isolation of a Bacterium That Reductively Dechlorinates Tetrachloroethene to Ethene

Maymó-Gatell, Xavier; Chien, Yueh-tyng; Gossett, James M.; Zinder, Stephen H.

doi:10.1126/science.276.5318.1568

Cited by 988 publications

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“…Strain 195 has a complex nutrition, requiring acetate, vitamins and extracts from mixed cultures 5 and its genome annotation predicted an incomplete pathway to methionine, lesions in the tricarboxylic acid cycle leading to glutamate, as well as incomplete pathways for the synthesis of vitamin B 12 , biotin and quinones 4 . Strain CBDB1 is able to grow in a defined medium containing only acetate and vitamins, yet these same lesions are still predicted to be present.…”

Section: Discussionmentioning

confidence: 99%

“…The recently described genome sequence of D. ethenogenes, strain 195 (ref. 4), an organism that reductively dechlorinates the solvents tetrachloroethene and trichloroethene to vinyl chloride and ethene 5 , reflects this specialization: although only 1.47-megabases (Mb) long, the genome possesses 17 rdhAB pairs potentially encoding reductive dehalogenases and genes predicted to encode five different hydrogenase complexes. We describe here the genome sequence of Dehalococcoides sp.…”

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Genome sequence of the chlorinated compound–respiring bacterium Dehalococcoides species strain CBDB1

et al. 2005

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Dehalococcoides species are strictly anaerobic bacteria, which catabolize many of the most toxic and persistent chlorinated aromatics and aliphatics by reductive dechlorination and are used for in situ bioremediation of contaminated sites. Our sequencing of the complete 1,395,502 base pair genome of Dehalococcoides strain CBDB1 has revealed the presence of 32 reductive-dehalogenase-homologous (rdh) genes, possibly conferring on the bacteria an immense dehalogenating potential. Most rdh genes were associated with genes encoding transcription regulators such as two-component regulatory systems or transcription regulators of the MarR-type. Four new paralog groups of rdh-associated genes without known function were detected. Comparison with the recently sequenced genome of Dehalococcoides ethenogenes strain 195 reveals a high degree of gene context conservation (synteny) but exceptionally high plasticity in all regions containing rdh genes, suggesting that these regions are under intense evolutionary pressure.In the past century, human activities have released large amounts of chlorinated organic compounds into the environment, and these compounds are among the most pervasive groundwater pollutants. Chloroorganics with fewer chlorines can usually be biodegraded by aerobic microorganisms, whereas more highly chlorinated ones can be reductively dechlorinated by organisms using them as electron acceptors for anaerobic respiration. Several microbial groups carry out respiratory reductive dechlorination 1 , but one genus, Dehalococcoides, seems particularly adapted to a unique niche, and the bacteria are only known to use chloroorganics as electron acceptors and hydrogen as an electron donor for growth. Several studies have now shown successful application of Dehalococcoides-containing cultures for in situ remediation of contaminated sites 2,3 . The recently described genome sequence of D. ethenogenes, strain 195 (ref. 4), an organism that reductively dechlorinates the solvents tetrachloroethene and trichloroethene to vinyl chloride and ethene 5 , reflects this specialization: although only 1.47-megabases (Mb) long, the genome possesses 17 rdhAB pairs potentially encoding reductive dehalogenases and genes predicted to encode five different hydrogenase complexes. We describe here the genome sequence of Dehalococcoides sp. strain CBDB1, a bacterium that has in many ways a different dechlorination spectrum from strain 195. For instance, strain CBDB1 (refs. 6,7) dechlorinated 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 2,3-dichloro-p-dibenzodioxin and the 'Seveso dioxin ' 2,3,7,8-tetrachloro-p-dibenzodioxin, but strain 195 (ref. 8) did not. In contrast to strain 195, strain CBDB1 did not dechlorinate tetrachloroethene past dichloroethene 6 . By sequencing a second Dehalococcoides genome, we can now show that strain CBDB1 has an even greater potential as a reductive dechlorinator than strain 195 and, in addition, the comparison of the two genomes with each other provides insights into the evolution of reductive dechlori...

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Genome sequence of the chlorinated compound–respiring bacterium Dehalococcoides species strain CBDB1

et al. 2005

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“…Chlorinated ethenes (PCE and TCE) can undergo reductive dechlorination to ethene (MaymoGatell et al, 1997). The sequential dechlorination requires anaerobic conditions (iron-reducing to methanogenic) (Hoelen and Reinhard, 2004;MaymoGatell et al, 1995;Wei and Finneran, 2011), a hydrogen donor (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…The degradation of PCE and TCE to cis-dichloroethene (cis-DCE) can be carried out by a variety of halogenating bacteria (such as Desulfitobacterium, Dehalobacter restrictus (Dhb) and Desulfuromonas (Middeldorp et al, 1999)), however, the degradation to ethene is only known to be carried out by the Dehalococcoides spp. (Dhc) (MaymoGatell et al, 1997). Dhc containing the gene tceA have been found to respire TCE and cis-DCE (Seshadri et al, 2005) whereas Dhc with the genes vcrA or bvcA respire cis-DCE and vinyl chloride (VC) (Muller et al, 2004;Sung et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Identification of chlorinated solvents degradation zones in clay till by high resolution chemical, microbial and compound specific isotope analysis

Damgaard

Bjerg

Bælum

et al. 2013

Journal of Contaminant Hydrology

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a b s t r a c tThe degradation of chlorinated ethenes and ethanes in clay till was investigated at a contaminated site (Vadsby, Denmark) by high resolution sampling of intact cores combined with groundwater sampling. Over decades of contamination, bioactive zones with degradation of trichloroethene (TCE) and 1,1,1-trichloroethane (1,1,1-TCA) to 1,2-cis-dichloroethene (cis-DCE) and 1,1-dichloroethane, respectively, had developed in most of the clay till matrix. Dehalobacter dominated over Dehalococcoides (Dhc) in the clay till matrix corresponding with stagnation of sequential dechlorination at cis-DCE. Sporadically distributed bioactive zones with partial degradation to ethene were identified in the clay till matrix (thickness from 0.10 to 0.22 m). In one sub-section profile the presence of Dhc with the vcrA gene supported the occurrence of degradation of cis-DCE and VC, and in another enriched δ 13 C for TCE, cis-DCE and VC documented degradation. Highly enriched δ 13 C for 1,1,1-TCA (25‰) and cis-DCE (−4‰) suggested the occurrence of abiotic degradation in a third sub-section profile. Due to fine scale heterogeneity the identification of active degradation zones in the clay till matrix depended on high resolution subsampling of the clay till cores. The study demonstrates that an integrated approach combining chemical analysis, molecular microbial tools and compound specific isotope analysis (CSIA) was required in order to document biotic and abiotic degradations in the clay till system.

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“…A decade ago, the first organism able to reduce the common groundwater contaminants, tetrachloroethene (PCE) and trichloroethene (TCE), completely to ethene was isolated (Maymo-Gatell et al, 1997). This microorganism, Dehalococcoides ethenogenes strain 195, uses TCE, cis-dichloroethene (cDCE), 1,1-dichloroethene (1,1-DCE), 1,2-dichloroethane (1,2-DCA) as electron acceptors for growth, but, significantly, it cannot use the known human carcinogen, vinyl chloride (VC), for growth (Maymo-Gatell et al, 1999.…”

Section: Introductionmentioning

confidence: 99%

Methods and Applications

Arveson

2002

Graduate Texts in Mathematics

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Dehalococcoides species are responsible for the reductive dehalogenation of an impressive range of common, persistent environmental contaminants. These microorganisms are difficult to both obtain and grow in pure culture, and so are often studied while they exist in consortia using molecular techniques. In particular, a significant number of quantitative real-time PCR (qPCR) assays targeting Dehalococcoides spp. have been reported. Initial qPCR methods targeted the 16S rRNA gene, however, because strains with the same 16S rRNA gene sequence can have different dehalogenating abilities, reductive dehalogenase genes are now emerging as the most appropriate qPCR target. Quantitative PCR has been critical to our current understanding of Dehalococcoides populations; it has provided information on their growth characteristics, dehalogenating abilities and effective use in bioremediation efforts. Future qPCR research directions will likely involve method standardization, as well as continued research on the functional genes associated with Dehalococcoides populations.

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Isolation of a Bacterium That Reductively Dechlorinates Tetrachloroethene to Ethene

Cited by 988 publications

References 18 publications

Genome sequence of the chlorinated compound–respiring bacterium Dehalococcoides species strain CBDB1

Genome sequence of the chlorinated compound–respiring bacterium Dehalococcoides species strain CBDB1

Identification of chlorinated solvents degradation zones in clay till by high resolution chemical, microbial and compound specific isotope analysis

Methods and Applications

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