| characterization of a defined 2,3,5, 6-tetrachlorobiphenyl-ortho-dechlorinating microbial community by comparative sequence analysis of genes coding for 16s rrna. | defined microbial communities were developed by combining selective enrichment with molecular monitoring of total community genes coding for 16s rrnas (16s rdnas) to identify potential polychlorinated biphenyl (pcb)-dechlorinating anaerobes that ortho dechlorinate 2,3, 5,6-tetrachlorobiphenyl. in enrichment cultures that contained a defined estuarine medium, three fatty acids, and sterile sediment, a clostridium sp. was predominant in the absence of added pcb, but undescribed species in the delt ... | 1998 | 9726883 |
| reductive dechlorination of chlorinated ethenes and 1, 2-dichloroethane by "dehalococcoides ethenogenes" 195. | "dehalococcoides ethenogenes" 195 can reductively dechlorinate tetrachloroethene (pce) completely to ethene (eth). when pce-grown strain 195 was transferred (2% [vol/vol] inoculum) into growth medium amended with trichloroethene (tce), cis-dichloroethene (dce), 1,1-dce, or 1,2-dichloroethane (dca) as an electron acceptor, these chlorinated compounds were consumed at increasing rates over time, which indicated that growth occurred. moreover, the number of cells increased when tce, 1,1-dce, or dca ... | 1999 | 10388710 |
| tetrachloroethene-dehalogenating bacteria. | tetrachloroethene is a frequent groundwater contaminant often persisting in the subsurface environments. it is recalcitrant under aerobic conditions because it is in a highly oxidized state and is not readily susceptible to oxidation. nevertheless, at least 15 organisms from different metabolic groups, viz. halorespirators (9), acetogens (2), methanogens (3) and facultative anaerobes (2), that are able to metabolize tetrachloroethene have been isolated as axenic cultures to-date. some of these o ... | 1999 | 10664879 |
| reductive dechlorination of tetrachloroethene to ethene by a two-component enzyme pathway. | two membrane-bound, reductive dehalogenases that constitute a novel pathway for complete dechlorination of tetrachloroethene (perchloroethylene [pce]) to ethene were partially purified from an anaerobic microbial enrichment culture containing dehalococcoides ethenogenes 195. when titanium (iii) citrate and methyl viologen were used as reductants, pce-reductive dehalogenase (pce-rdase) (51 kda) dechlorinated pce to trichloroethene (tce) at a rate of 20 micromol/min/mg of protein. tce-reductive de ... | 1998 | 10671186 |
| 16s rrna gene-based detection of tetrachloroethene-dechlorinating desulfuromonas and dehalococcoides species. | members of the genera desulfuromonas and dehalococcoides reductively dechlorinate tetrachloroethene (pce) and trichloroethene. two primer pairs specific to hypervariable regions of the 16s rrna genes of the dehalococcoides group (comprising dehalococcoides ethenogenes and dehalococcoides sp. strain fl2) and the acetate-oxidizing, pce-dechlorinating desulfuromonas group (comprising desulfuromonas sp. strain bb1 and desulfuromonas chloroethenica) were designed. the detection threshold of a nested ... | 2000 | 10742213 |
| trichloroethene reductive dehalogenase from dehalococcoides ethenogenes: sequence of tcea and substrate range characterization. | the anaerobic bacterium dehalococcoides ethenogenes is the only known organism that can completely dechlorinate tetrachloroethene or trichloroethene (tce) to ethene via dehalorespiration. one of two corrinoid-containing enzymes responsible for this pathway, tce reductive dehalogenase (tce-rdase) catalyzes the dechlorination of tce to ethene. tce-rdase dehalogenated 1,2-dichloroethane and 1, 2-dibromoethane to ethene at rates of 7.5 and 30 micromol/min/mg, respectively, similar to the rates for t ... | 2000 | 11097881 |
| bacterial dehalorespiration with chlorinated benzenes. | chlorobenzenes are toxic, highly persistent and ubiquitously distributed environmental contaminants that accumulate in the food chain. the only known microbial transformation of 1,2,3,5-tetrachlorobenzene (tecb) and higher chlorinated benzenes is the reductive dechlorination to lower chlorinated benzenes under anaerobic conditions observed with mixed bacterial cultures. the lower chlorinated benzenes can subsequently be mineralized by aerobic bacteria. here we describe the isolation of the oxyge ... | 2000 | 11117744 |
| phylogenetic analyses of two "archaeal" genes in thermotoga maritima reveal multiple transfers between archaea and bacteria. | the genome sequence of thermotoga maritima revealed that 24% of its open reading frames (orfs) showed the highest similarity scores to archaeal genes in blast analyses. here we screened 16 strains from the genus thermotoga and other related thermotogales for the occurrence of two of these "archaeal" genes: the gene encoding the large subunit of glutamate synthase (gltb) and the myo-inositol 1p synthase gene (ino1). both genes were restricted to the thermotoga species within the thermotogales. th ... | 2001 | 11230537 |
| reductive dechlorination of cis-1,2-dichloroethene and vinyl chloride by "dehalococcoides ethenogenes". | cis-dichloroethene (dce) and vinyl chloride (vc) often accumulate in contaminated aquifers in which tetrachloroethene (pce) or trichloroethene (tce) undergo reductive dechlorination. "dehalococcoides ethenogenes" strain 195 is the first isolate capable of dechlorinating chloroethenes past cis-dce. strain 195 could utilize commercially synthesized cis-dce as an electron acceptor, but doses greater than 0.2 mmol/l were inhibitory, especially to pce utilization. to test whether the cis-dce itself w ... | 2001 | 11351722 |
| assessment of indigenous reductive dechlorinating potential at a tce-contaminated site using microcosms, polymerase chain reaction analysis, and site data. | a combination of microcosm studies, polymerase chain reaction (pcr) analysis, and site data was used to assess the indigenous reductive dechlorinating potential in a trichloroethene (tce)-contaminated aquifer at cape canaveral air station, florida. sediment and groundwater were obtained from two distinct locations approximately 10 m apart. microcosm studies were performed to assess dechlorinating activity under a variety of nutrient and electron donor amendment conditions. most live microcosms c ... | 2001 | 11355200 |
| further biogeochemical characterization of a trichloroethene-contaminated fractured dolomite aquifer: electron source and microbial communities involved in reductive dechlorination. | a recent article presented geochemical and microbial evidence establishing metabolic adaptation to and in-situ reductive dechlorination of trichloroethene (tce) in a fractured dolomite aquifer. this study was designed to further explore site conditions and microbial populations and to explain previously reported enhancement of reductive dechlorination by the addition of pulverized dolomite to laboratory microcosms. a survey of groundwater geochemical parameters (chlorinated ethenes, ethene, h2, ... | 2001 | 11757600 |
| molecular analysis of dehalococcoides 16s ribosomal dna from chloroethene-contaminated sites throughout north america and europe. | the environmental distribution of dehalococcoides group organisms and their association with chloroethene-contaminated sites were examined. samples from 24 chloroethene-dechlorinating sites scattered throughout north america and europe were tested for the presence of members of the dehalococcoides group by using a pcr assay developed to detect dehalococcoides 16s rrna gene (rdna) sequences. sequences identified by sequence analysis as sequences of members of the dehalococcoides group were detect ... | 2002 | 11823182 |
| identification of a microorganism that links its growth to the reductive dechlorination of 2,3,5,6-chlorobiphenyl. | anaerobic bacteria reductively dechlorinate polychlorinated biphenyls (pcbs) in aquatic sediments, but these microorganisms remain uncultured and, until now, unidentified. through denaturing gradient gel electrophoresis (dgge) of 16s rdna from a highly enriched ortho-pcb dechlorinating culture, the growth of a single microorganism was shown to be dependent upon the presence and dechlorination of 2,3,5,6-tetrachlorobiphenyl. this is the first identification of a microorganism that catalyses the r ... | 2001 | 11846760 |
| phylogenetic characterization of microbial communities that reductively dechlorinate tce based upon a combination of molecular techniques. | an anaerobic microbial consortium (referred to as anas) that reductively dechlorinates trichloroethene (tce) completely to ethene with the transient production of cisdichloroethene (cdce) and vinyl chloride was enriched from contaminated soil obtained from alameda naval air station. anas uses lactate as its electron donor and has been functionally stable for over 2 years. following a brief exposure to oxygen, a subculture (designated vcc) derived from anas could dechlorinate tce only to vinyl ch ... | 2002 | 12099461 |
| a green nonsulfur bacterium, dehalococcoides ethenogenes, with the lexa binding sequence found in gram-positive organisms. | dehalococcoides ethenogenes is a member of the physiologically diverse division of green nonsulfur bacteria. using a tblastn search, the d. ethenogenes lexa gene has been identified, cloned, and expressed and its protein has been purified. mobility shift assays revealed that the d. ethenogenes lexa protein specifically binds to both its own promoter and that of the uvra gene, but not to the reca promoter. our results demonstrate that the d. ethenogenes lexa binding site is gaacn(4)gttc, which is ... | 2002 | 12374844 |
| occurrence of several genes encoding putative reductive dehalogenases in desulfitobacterium hafniense/frappieri and dehalococcoides ethenogenes. | desulfitobacterium frappieri pcp-1 has the capacity to dehalogenate several halogenated aromatic compounds by reductive dehalogenation, however, the genes encoding the enzymes involved in such processes have not yet been identified. using a degenerate oligonucleotide corresponding to a conserved sequence of cpra/pcea reductive dehalogenases, a cpra-like gene fragment was amplified by pcr from this bacterial strain. a desulfitobacterium frappieri pcp-1 cosmid library was screened with the pcr pro ... | 2002 | 12381026 |
| comparison of anaerobic dechlorinating enrichment cultures maintained on tetrachloroethene, trichloroethene, cis-dichloroethene and vinyl chloride. | an anaerobic mixed microbial culture was enriched from soil and groundwater taken from a site contaminated with trichloroethene (tce). this enrichment culture was divided into four subcultures amended separately with either perchloroethene (pce), tce, cis-dichloroethene (cdce) or vinyl chloride (vc). in each of the four subcultures, the chlorinated ethenes were rapidly, consistently, and completely converted to ethene at rates of 30-50 micromol/l of culture per day, or an average 160 micro-elect ... | 2002 | 12420924 |
| field demonstration of successful bioaugmentation to achieve dechlorination of tetrachloroethene to ethene. | a laboratory microcosm study and a pilot scale field test were conducted to evaluate biostimulation and bioaugmentation to dechlorinate tetrachloroethene (pce) to ethene at kelly air force base. the site groundwater contained about 1 mg/l of pce and lower amounts of trichloroethene (tce) and cis-1,2-dichloroethene (cdce). laboratory microcosms inoculated with soil and groundwater from the site exhibited partial dechlorination of tce to cdce when amended with lactate or methanol. following the ad ... | 2002 | 12523427 |
| reductive dehalogenation of chlorinated dioxins by an anaerobic bacterium. | polychlorinated dibenzo-p-dioxins and dibenzofurans (pcdds and pcdfs) are among the most notorious environmental pollutants. some congeners, particularly those with lateral chlorine substitutions at positions 2, 3, 7 and 8, are extremely toxic and carcinogenic to humans. one particularly promising mechanism for the detoxification of pcdds and pcdfs is microbial reductive dechlorination. so far only a limited number of phylogenetically diverse anaerobic bacteria have been found that couple the re ... | 2003 | 12540897 |
| growth of a dehalococcoides-like microorganism on vinyl chloride and cis-dichloroethene as electron acceptors as determined by competitive pcr. | a competitive pcr (cpcr) assay targeting 16s ribosomal dna was developed to enumerate growth of a dehalococcoides-like microorganism, bacterium vs, from a mixed culture catalyzing the reductive dehalogenation of cis-1,2-dichloroethene (cdce) and vinyl chloride (vc), with hydrogen being used as an electron donor. the growth of bacterium vs was found to be coupled to the dehalogenation of vc and cdce, suggesting unique metabolic capabilities. the average growth yield was (5.2 +/- 1.5) x 10(8) copi ... | 2003 | 12571017 |
| complete detoxification of vinyl chloride by an anaerobic enrichment culture and identification of the reductively dechlorinating population as a dehalococcoides species. | a major obstacle in the implementation of the reductive dechlorination process at chloroethene-contaminated sites is the accumulation of the intermediate vinyl chloride (vc), a proven human carcinogen. to shed light on the microbiology involved in the final critical dechlorination step, a sediment-free, nonmethanogenic, vc-dechlorinating enrichment culture was derived from tetrachloroethene (pce)-to-ethene-dechlorinating microcosms established with material from the chloroethene-contaminated bac ... | 2003 | 12571022 |
| kinetic and phylogenetic characterization of an anaerobic dechlorinating microbial community. | the reductive dechlorination (rd) of tetrachloroethene (pce) to vinyl chloride (vc) and, to a lesser extent, to ethene (eth) by an anaerobic microbial community has been investigated by studying the processes and kinetics of the main physiological components of the consortium. molecular hydrogen, produced by methanol-utilizing acetogens, was the electron donor for the pce rd to vc and eth without forming any appreciable amount of other chlorinated intermediates and in the near absence of methano ... | 2003 | 12624208 |
| phylogenetic analysis of bacterial populations in an anaerobic microbial consortium capable of degrading saturation concentrations of tetrachloroethylene. | an anaerobic microbial consortium able to biodegrade saturation levels of perchloroethylene (pce) in a column containing a source zone of pce was examined phylogenetically to determine microbial community structure and spatial variation in relation to the pce source. the consortium was comprised of at least 34 members with 7 organisms sharing affiliations with known respiratory or cometabolic dechlorinators. seven other organisms had their closest phylogenetic relative detected in other environm ... | 2003 | 12674344 |
| specific detection of dehalococcoides species by fluorescence in situ hybridization with 16s rrna-targeted oligonucleotide probes. | dehalococcoides ethenogenes is the only known cultivated organism capable of complete dehalogenation of tetrachloroethene (pce) to ethene. the prevalence of dehalococcoides species in the environment and their association with complete dehalogenation of chloroethenes suggest that they play an important role in natural attenuation of chloroethenes and are promising candidates for engineered bioremediation of these contaminants. both natural attenuation and bioremediation require reliable and sens ... | 2003 | 12732561 |
| reductive dehalogenation of chlorobenzene congeners in cell extracts of dehalococcoides sp. strain cbdb1. | enzymatic reductive dehalogenation of tri-, tetra-, penta-, and hexachlorobenzenes was demonstrated in cell extracts with low protein concentration (0.5 to 1 micro g of protein/ml) derived from the chlorobenzene-respiring anaerobe dehalococcoides sp. strain cbdb1. 1,2,3-trichlorobenzene dehalogenase activity was associated with the membrane fraction. light-reversible inhibition by alkyl iodides indicated the presence of a corrinoid cofactor. | 2003 | 12732577 |
| inoculation of a dnapl source zone to initiate reductive dechlorination of pce. | the ability to inoculate a pce-napl source zone with no prior dechlorinating activity was examined using a near field-scale simulated aquifer. a known mass of pce was added to establish a source zone, and the groundwater was depleted of oxygen using acetate and lactate prior to culture addition. an active and stable dechlorinating culture was used as an inoculum, and dechlorination activity was observed within 2 weeks following culture transfer. pce reduction to tce and cis-dce was observed init ... | 2003 | 12831039 |
| dehalorespiration with hexachlorobenzene and pentachlorobenzene by dehalococcoides sp. strain cbdb1. | the chlororespiring anaerobe dehalococcoides sp. strain cbdb1 used hexachlorobenzene and pentachlorobenzene as electron acceptors in an energy-conserving process with hydrogen as electron donor. previous attempts to grow dehalococcoides sp. strain cbdb1 with hexachlorobenzene or pentachlorobenzene as electron acceptors failed if these compounds were provided as solutions in hexadecane. however, dehalococcoides sp. strain cbdb1 was able to grow with hexachlorobenzene or pentachlorobenzene when ad ... | 2003 | 14564452 |
| vinyl bromide as a surrogate for determining vinyl chloride reductive dechlorination potential. | site evaluation for bioremediation of chlorinated ethenes may need treatability studies to assess the reductive dechlorination potential of vinyl chloride (vc). dehalogenation of vinyl bromide (vb) was investigated as a surrogate measurement for the dechlorination potential of vc. vb dehalogenation rates and kinetics were studied and compared with those of vc by a methanogenic reductive dechlorinating enrichment culture that was dominated by dehalococcoides species and by microcosms from two chl ... | 2003 | 14572093 |
| detection and quantitative estimation of dehalococcoides spp. in a dechlorinating bioreactor by a combination of fluorescent in situ hybridisation (fish) and kinetic analysis. | the unique capacity of dehalococcoides ethenogenes of completely dechlorinating the common groundwater pollutant tetrachloroethene (pce) to the harmless ethene makes this microorganism very attractive for application in natural or engineered bioremediation systems. in this study, the qualitative and quantitative determination of dehalococcoides spp. in a lab-scale bioreactor was performed based on the combination of fluorescent in situ hybridisation (fish) for specific detection, and kinetic bat ... | 2004 | 14685786 |
| analysis and comparison of the microbial community structures of two enrichment cultures capable of reductively dechlorinating tce and cis-dce. | in order to study the effect of different chloroethenes (electron acceptors) on the bacterial composition of dechlorinating communities, two reductive dechlorinating enrichment cultures were developed that were able to reduce trichloroethene (tce) and cis-1,2-dichloroethene (cis-dce) to ethene using hydrogen as electron donor, respectively. the inoculum for the cultures was material from a methanogenic fluidized bed reactor (fbr), which was originally seeded with digester sludge and showed a sta ... | 2004 | 14686940 |
| development of degenerate and specific pcr primers for the detection and isolation of known and putative chloroethene reductive dehalogenase genes. | degenerate and specific pcr primers were designed for the detection of chloroethene reductive dehalogenases (ce-rdase), the key enzymes of chloroethene dehalorespiration, based on sequence information of three ce-rdases and three chlorophenol (cp) rdases. for the design of the degenerate primers, seven conserved amino-acid blocks identified with different bioinformatic tools were used. for one block degenerate, primers containing a 5'-consensus clamp region specific for ce-rdases and a 3'-end de ... | 2004 | 14706755 |
| hydrogen thresholds as indicators of dehalorespiration in constructed treatment wetlands. | anaerobic degradation of cis-1,2-dichloroethene (cis-1,2-dce) and 1,2-dichloroethane (1,2-dca) was studied in microcosms derived from a laboratory-scale upflow treatment wetland system used to biodegrade chlorinated compounds present in groundwater from a superfund site. dechlorination kinetics of cis-1,2-dce (0.94-1.57 d(-1)) and 1,2-dca (0.15-0.71 d(-1)) were rapid, and degradation proceeded to completion with ethene or ethane as terminal dechlorination products. hydrogen concentrations, measu ... | 2004 | 14998014 |
| dechlorination of pce in the presence of fe0 enhanced by a mixed culture containing two dehalococcoides strains. | a mixed culture capable of supplying its energy requirements by the oxidation of zero-valent iron (fe0) and concomitant reduction of chlorinated ethenes was established. the culture contained dehalococcoides species as determined by polymerase chain reaction (pcr) with genus specific primers. the use of a newly designed ardra procedure and subsequent sequencing revealed the presence of two dehalococcoides strains, one closely related to dehalococcoides ethenogenes strain 195, a bacterium respiri ... | 2004 | 15013671 |
| degradation of 1,1,2,2-tetrachloroethane and accumulation of vinyl chloride in wetland sediment microcosms and in situ porewater: biogeochemical controls and associations with microbial communities. | the biodegradation pathways of 1,1,2,2-tetrachloroethane (teca) and 1,1,2-trichloroethane (112tca) and the associated microbial communities in anaerobic wetland sediments were evaluated using concurrent geochemical and genetic analyses over time in laboratory microcosm experiments. experimental results were compared to in situ porewater data in the wetland to better understand the factors controlling daughter product distributions in a chlorinated solvent plume discharging to a freshwater tidal ... | 2004 | 15068871 |
| flux and product distribution during biological treatment of tetrachloroethene dense non-aqueous-phase liquid. | flux in non-aqueous-phase liquid (napl)-contaminated systems containing active microbial populations (including dehalococcoides sp.) was investigated using a quantitative mass balance and phase distribution approach. batch systems containing mixed napl with an initial tetrachloroethene (pce) mole fraction ranging from 0.1 to 0.4 provided a means for comparing systems where mass transfer and aqueous concentration were controlled by the initial napl composition. although the use of mixed napl with ... | 2004 | 15112802 |
| dehalococcoides ethenogenes strain 195 reductively dechlorinates diverse chlorinated aromatic pollutants. | dehalococcoides ethenogenes strain 195 dechlorinates tetrachloroethene to vinyl chloride and ethene, and its genome has been found to contain up to 17 putative dehalogenase gene homologues, suggesting diverse dehalogenation ability. we amended pure or mixed cultures containing d. ethenogenes strain 195 with 1,2,3,4-tetrachlorodibenzo-p-dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin, 2,3-dichlorodibenzo-p-dioxin, 1,2,3,4-tetrachlorodibenzofuran, 2,3,4,5,6-pentachlorobiphenyl, 1,2,3,4-tetrachloronaph ... | 2004 | 15112809 |
| development of a real-time pcr method for quantification of the three genera dehalobacter, dehalococcoides, and desulfitobacterium in microbial communities. | we developed standard curves based on plasmids containing a 16s rrna gene of a member of one of the three genera dehalobacter, desulfitobacterium, and dehalococcoides. a large difference in amplification efficiency between the standard curves was observed ranging from 1.5 to 2.0. the total eubacterial 16s rrna gene copy number determined in a sample dna by using eubacterial primers and the three standard curves led to differences in the estimated copy numbers of a factor up to 73. however, the a ... | 2004 | 15134884 |
| a gene from the mesophilic bacterium dehalococcoides ethenogenes encodes a novel mannosylglycerate synthase. | mannosylglycerate (mg) is a common compatible solute found in thermophilic and hyperthermophilic prokaryotes. in this study we characterized a mesophilic and bifunctional mannosylglycerate synthase (mgsd) encoded in the genome of the bacterium dehalococcoides ethenogenes. mgsd encodes two domains with extensive homology to mannosyl-3-phosphoglycerate synthase (mpgs, ec 2.4.1.217) and to mannosyl-3-phosphoglycerate phosphatase (mpgp, ec 3.1.3.70), which catalyze the consecutive synthesis and deph ... | 2004 | 15205409 |
| populations implicated in anaerobic reductive dechlorination of 1,2-dichloropropane in highly enriched bacterial communities. | 1,2-dichloropropane (1,2-d), a widespread groundwater contaminant, can be reductively dechlorinated to propene by anaerobic bacteria. to shed light on the populations involved in the detoxification process, a comprehensive 16s rrna gene-based bacterial community analysis of two enrichment cultures derived from geographically distinct locations was performed. analysis of terminal restriction fragments, amplicons obtained with dechlorinator-specific pcr primers, and enumeration with quantitative r ... | 2004 | 15240287 |
| molecular identification of the catabolic vinyl chloride reductase from dehalococcoides sp. strain vs and its environmental distribution. | reductive dehalogenation of vinyl chloride (vc) to ethene is the key step in complete anaerobic degradation of chlorinated ethenes. vc-reductive dehalogenase was partially purified from a highly enriched culture of the vc-respiring dehalococcoides sp. strain vs. the enzyme reduced vc and all dichloroethene (dce) isomers, but not tetrachloroethene (pce) or trichloroethene (tce), at high rates. by using reversed genetics, the corresponding gene (vcra) was isolated and characterized. based on the p ... | 2004 | 15294827 |
| multiple nonidentical reductive-dehalogenase-homologous genes are common in dehalococcoides. | degenerate primers were used to amplify large fragments of reductive-dehalogenase-homologous (rdh) genes from genomic dna of two dehalococcoides populations, the chlorobenzene- and dioxin-dechlorinating strain cbdb1 and the trichloroethene-dechlorinating strain fl2. the amplicons (1,350 to 1,495 bp) corresponded to nearly complete open reading frames of known reductive dehalogenase genes and short fragments (approximately 90 bp) of genes encoding putative membrane-anchoring proteins. cloning and ... | 2004 | 15345412 |
| characterization of a highly enriched dehalococcoides-containing culture that grows on vinyl chloride and trichloroethene. | a highly enriched culture that reductively dechlorinates trichloroethene (tce), cis-1,2-dichloroethene (cdce), and vinyl chloride (vc) to ethene without methanogenesis is described. the dehalococcoides strain in this enrichment culture had a yield of (5.6 +/- 1.4) x 10(8) 16s rrna gene copies/micromol of cl(-) when grown on vc and hydrogen. unlike the other vc-degrading cultures described in the literature, strains vs and bav1, this culture maintained the ability to grow on tce with a yield of ( ... | 2004 | 15345442 |
| batch-test study on the dechlorination of 1,1,1-trichloroethane in contaminated aquifer material by zero-valent iron. | chlorinated aliphatic hydrocarbons are common groundwater contaminants. one possible remediation option is in-situ reductive dechlorination by zero-valent iron, either by direct injection or as reactive barriers. chlorinated ethenes (tetrachloroethene: pce; trichloroethene: tce) have received extensive attention in this context. however, another common groundwater pollutant, 1,1,1-trichlorethane (tca), has attracted much less attention. we studied tca reduction by three types of granular zero-va ... | 2004 | 15358490 |
| anaerobic microbial reductive dechlorination of tetrachloroethene to predominately trans-1,2-dichloroethene. | while most sites and all characterized pce and tce dechlorinating anaerobic bacteria produce cis-dce as the major dce isomer, significant amounts of trans-dce are found in the environment. we have obtained microcosms from some sites and enrichment cultures that produce more trans-dce than cis-dce. these cultures reductively dechlorinated pce and tce to trans-dce and cis-dce simultaneously and in a ratio of 3(+/-0.5):1 that was stable through serial transfers with a variety of electron donors and ... | 2004 | 15382856 |
| genetic identification of a putative vinyl chloride reductase in dehalococcoides sp. strain bav1. | dehalococcoides sp. strain bav1 couples growth with the reductive dechlorination of vinyl chloride (vc) to ethene. degenerate primers targeting conserved regions in reductive dehalogenase (rdase) genes were designed and used to pcr amplify putative rdase genes from strain bav1. seven unique rdase gene fragments were identified. transcription analysis of vc-grown bav1 cultures suggested that bvca was involved in vc reductive dechlorination, and the complete sequence of bvca was obtained. bvca was ... | 2004 | 15466590 |
| comparative evaluation of chloroethene dechlorination to ethene by dehalococcoides-like microorganisms. | reductive dehalogenation of tetrachloroethene (pce), trichloroethene (tce), cis-1,2-dichloroethene (dce), and vinyl chloride (vc) was examined in four cultures containing dehalococcoides-like microorganisms. dechlorination and growth kinetics were compared using a monod growth-rate model for multiple electron acceptor usage with competition. included were the victoria mixed culture containing dehalococcoides species strain vs (from victoria, tx), the mixed culture kb-1/vc (from southern ontario) ... | 2004 | 15487786 |
| studies on hydrogenase activity and chlorobenzene respiration in dehalococcoides sp. strain cbdb1. | hydrogen oxidation and electron transport were studied in the chlorobenzene-utilizing anaerobe dehalococcoides sp. strain cbdb1. while cu(2+) and hg(2+) ions irreversibly inhibited hydrogenase activity in intact cells, ni(2+) ions inhibited reversibly. about 80% of the initial hydrogenase activity was inactivated within 30 s when the cells were exposed to air. in contrast, hydrogenase was active at a redox potential of +10 mv when this redox potential was established anoxically with a redox indi ... | 2004 | 15490122 |
| molecular characterization of a dechlorinating community resulting from in situ biostimulation in a trichloroethene-contaminated deep, fractured basalt aquifer and comparison to a derivative laboratory culture. | sodium lactate additions to a trichloroethene (tce) residual source area in deep, fractured basalt at a u.s. department of energy site have resulted in the enrichment of the indigenous microbial community, the complete dechlorination of nearly all aqueous-phase tce to ethene, and the continued depletion of the residual source since 1999. the bacterial and archaeal consortia in groundwater obtained from the residual source were assessed by using pcr-amplified 16s rrna genes. a clone library of ba ... | 2004 | 15574933 |
| genome sequence of the pce-dechlorinating bacterium dehalococcoides ethenogenes. | dehalococcoides ethenogenes is the only bacterium known to reductively dechlorinate the groundwater pollutants, tetrachloroethene (pce) and trichloroethene, to ethene. its 1,469,720-base pair chromosome contains large dynamic duplicated regions and integrated elements. genes encoding 17 putative reductive dehalogenases, nearly all of which were adjacent to genes for transcription regulators, and five hydrogenase complexes were identified. these findings, plus a limited repertoire of other metabo ... | 2005 | 15637277 |
| assessment of natural or enhanced in situ bioremediation at a chlorinated solvent-contaminated aquifer in italy: a microcosm study. | a microcosm study was used to assess the potential for in situ natural or enhanced bioremediation at a chloroethane- (i.e., tetrachloroethane, teca) and chloroethene-contaminated (i.e., tetrachloroethene, pce; trichloroethene, tce) groundwater in northern italy. all the live microcosms were positive for dechlorination, indicating the presence of an active native dechlorinating population in the subsurface. all the tested electron donors (i.e., yeast extract, lactate, butyrate, hydrogen) promoted ... | 2005 | 15661281 |
| enrichment of anaerobic polychlorinated biphenyl dechlorinators from sediment with iron as a hydrogen source. | little is known about anaerobic polychlorinated biphenyl (pcb) dechlorination, although it is believed that some microorganisms are capable of respiring pcbs, gaining energy for growth from pcb dechlorination. if this is the case, the amendment of appropriate electron donors to contaminated sediment should stimulate dechlorination. the effect of elemental iron (fe0) addition, an easily amended electron donor, on the microbial dechlorination of the pcb congeners 3,4,5-trichlorobiphenyl (3,4,5-cb) ... | 2004 | 15707629 |
| characterization of hydrogenase and reductive dehalogenase activities of dehalococcoides ethenogenes strain 195. | dehalococcoides ethenogenes strain 195 reductively dechlorinates tetrachloroethene (pce) and trichloroethene (tce) to vinyl chloride and ethene using h2 as an electron donor. pce- and tce-reductive dehalogenase (rd) activities were mainly membrane associated, whereas only about 20% of the hydrogenase activity was membrane associated. experiments with methyl viologen (mv) were consistent with a periplasmic location for the rds or a component feeding electrons to them. the protonophore uncoupler t ... | 2005 | 15746376 |
| indications for acquisition of reductive dehalogenase genes through horizontal gene transfer by dehalococcoides ethenogenes strain 195. | the genome of dehalococcoides ethenogenes strain 195, an anaerobic dehalorespiring bacterium, contains 18 copies of putative reductive dehalogenase genes, including the well-characterized tcea gene, whose gene product functions as the key enzyme in the environmentally important dehalorespiration process. the genome of d. ethenogenes was analyzed using a bioinformatic tool based on the frequency of oligonucleotides. the results in the form of a genomic signature revealed several local disruptions ... | 2005 | 15932990 |
| a pcr-based specific assay reveals a population of bacteria within the chloroflexi associated with the reductive dehalogenation of polychlorinated biphenyls. | polychlorinated biphenyls (pcbs) accumulate and persist in sediments posing a risk to human health and the environment. highly chlorinated pcbs are reductively dechlorinated in anaerobic sediments and two bacteria, designated o-17 and df-1, from a novel phylogenetic group that reductively dechlorinate pcbs have recently been identified. however, there is a paucity of knowledge about the distribution, diversity and ecology of pcb-dechlorinating bacteria due to difficulty in obtaining pure culture ... | 2005 | 15942010 |
| fundamental things apply: the case of dehalococcoides ethenogenes. | | 2005 | 16052463 |
| phylogenetic characterization of a polychlorinated-dioxin- dechlorinating microbial community by use of microcosm studies. | microcosms capable of reductive dechlorination of polychlorinated dibenzo-p-dioxins/dibenzofurans (pcdd/fs) were constructed in glass bottles by seeding them with a polluted river sediment and incubating them anaerobically with an organic medium. all of the pcdd/f congeners detected were equally reduced without the accumulation of significant amounts of less-chlorinated congeners as the intermediate or end products. alternatively, large amounts of catechol and salicylic acid were produced in the ... | 2005 | 16085820 |
| isolation and characterization of dehalococcoides sp. strain fl2, a trichloroethene (tce)- and 1,2-dichloroethene-respiring anaerobe. | a strictly anaerobic bacterium was isolated from tetrachloroethene (pce)-to-ethene dechlorinating microcosms established with river sediment without prior exposure to chlorinated solvents. the isolation procedure included the addition of 2-bromoethanesulfonate to select against methanogenic archaea, >50 consecutive 1-2% (v/v) transfers to reduced mineral salts medium amended with trichloroethene (tce), acetate, and hydrogen, the addition of ampicillin, and the dilution-to-extinction principle. c ... | 2005 | 16104866 |
| identification of microorganisms involved in reductive dehalogenation of chlorinated ethenes in an anaerobic microbial community. | in this study, we report on phylogenetic and physiological characterization of an anaerobic culture capable of reductive dehalogenation of tetrachloroethene (pce) obtained from a pce-contaminated site. the culture was enriched using different combinations of electron donors (hydrogen and acetate) and electron acceptors (pce, cis-1,2-dichloroethene (cdce) and controls without chlorinated ethenes). the resulting subcultures were analyzed using three different approaches: chemical analysis to docum ... | 2005 | 16112710 |
| genome sequence of the chlorinated compound-respiring bacterium dehalococcoides species strain cbdb1. | 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 wer ... | 2005 | 16116419 |
| anaerobic transformation of tetrachloroethane, perchloroethylene, and their mixtures by mixed-cultures enriched from contaminated soils and sediments. | the focus of this research was to investigate the anaerobic transformation of tetrachloroethane (teca), perchloroethylene (pce), and their mixtures by mixed cultures enriched from contaminated soils or sediments. batch transformation studies were conducted using teca (60 microm), pce (60 microm), or teca + pce (each added at 60 microm) as electron acceptor(s) and h2 + acetate (each added at 3 mm) or butyrate (3mm) as electron donor(s). a dehalococcoides spp.-containing, sediment-enrichment dechl ... | 2005 | 16180450 |
| enrichment, cultivation, and detection of reductively dechlorinating bacteria. | strategies and procedures for enriching, isolating, and cultivating reductively dechlorinating bacteria that use chloroorganic compounds as metabolic electron acceptors from environmental samples are described. further, nucleic acid-based approaches used to detect and quantify dechlorinator (i.e., dehalococcoides)-specific genes are presented. | 2005 | 16260286 |
| transcriptional expression of the tcea gene in a dehalococcoides-containing microbial enrichment. | dynamic changes in the transcriptional expression of the tcea gene, which encodes a trichloroethene reductive dehalogenase, were characterized in a dehalococcoides-containing microbial enrichment culture. expression was quantified by real-time pcr as the number of tcea transcripts per tcea gene. expression of tcea increased 40-fold after chlorinated ethene-starved cells were exposed to trichloroethene (tce), cis-dichloroethene (dce), or 1,1-dce but did not increase after exposure to tetrachloroe ... | 2005 | 16269753 |
| phylogenetic analysis of tce-dechlorinating consortia enriched on a variety of electron donors. | two rapidly fermented electron donors, lactate and methanol, and two slowly fermented electron donors, propionate and butyrate, were selected for enrichment studies to evaluate the characteristics of anaerobic microbial consortia that reductively dechlorinate tce to ethene. each electron donor enrichment subculture demonstrated the ability to dechlorinate tce to ethene through several serial transfers. microbial community analyses based upon 16s rdna, including terminal restriction fragment leng ... | 2005 | 16294874 |
| sequential reductive dechlorination of meta-chlorinated polychlorinated biphenyl congeners in sediment microcosms by two different chloroflexi phylotypes. | three species within a deeply branching cluster of the chloroflexi are the only microorganisms currently known to anaerobically transform polychlorinated biphenyls (pcbs) by the mechanism of reductive dechlorination. a selective pcr primer set was designed that amplifies the 16s rrna genes of a monophyletic group within the chloroflexi including dehalococcoides spp. and the o-17/df-1 group. assays for both qualitative and quantitative analyses by denaturing gradient gel electrophoresis and most ... | 2005 | 16332789 |
| multiple reductive-dehalogenase-homologous genes are simultaneously transcribed during dechlorination by dehalococcoides-containing cultures. | degenerate primers were used to amplify 14 distinct reductive-dehalogenase-homologous (rdh) genes from the dehalococcoides-containing mixed culture kb1. most of the corresponding predicted proteins were highly similar (97 to >99% amino acid identity) to previously reported dehalococcoides reductive dehalogenases. to examine the differential transcription of these rdh genes, kb1 was split into five subcultures amended with either trichloroethene, cis-1,2-dichloroethene, vinyl chloride, 1,2-dichlo ... | 2005 | 16332811 |
| phospholipid furan fatty acids and ubiquinone-8: lipid biomarkers that may protect dehalococcoides strains from free radicals. | dehalococcoides species have a highly restricted lifestyle and are only known to derive energy from reductive dehalogenation reactions. the lipid fraction of two dehalococcoides isolates, strains bav1 and fl2, and a tetrachloroethene-to-ethene-dechlorinating dehalococcoides-containing consortium were analyzed for neutral lipids and phospholipid fatty acids. unusual phospholipid modifications, including the replacement of unsaturated fatty acids with furan fatty acids, were detected in both dehal ... | 2005 | 16332831 |
| growth of dehalobacter and dehalococcoides spp. during degradation of chlorinated ethanes. | mixed anaerobic microbial subcultures enriched from a multilayered aquifer at a former chlorinated solvent disposal facility in west louisiana were examined to determine the organism(s) involved in the dechlorination of the toxic compounds 1,2-dichloroethane (1,2-dca) and 1,1,2-trichloroethane (1,1,2-tca) to ethene. sequences phylogenetically related to dehalobacter and dehalococcoides, two genera of anaerobic bacteria that are known to respire with chlorinated ethenes, were detected through clo ... | 2006 | 16391074 |
| the reductive dechlorination of 2,3,4,5-tetrachlorobiphenyl in three different sediment cultures: evidence for the involvement of phylogenetically similar dehalococcoides-like bacterial populations. | anaerobic cultures capable of reductively dechlorinating 2,3,4,5-tetrachlorobiphenyl (cb) were enriched from three different sediments, one estuarine, one marine and one riverine. two different electron donors were used in enrichments with the estuarine sediment (elemental iron or a mixture of fatty acids). the removal of doubly flanked meta and para chlorines to form 2,3,5-cb and 2,4,5-cb was observed in all cultures. bacterial community analysis of pcr-amplified 16s rrna gene fragments reveale ... | 2006 | 16420633 |
| characterization of the biosynthetic pathway of glucosylglycerate in the archaeon methanococcoides burtonii. | the pathway for the synthesis of the organic solute glucosylglycerate (gg) is proposed based on the activities of the recombinant glucosyl-3-phosphoglycerate synthase (gpgs) and glucosyl-3-phosphoglycerate phosphatase (gpgp) from methanococcoides burtonii. a mannosyl-3-phosphoglycerate phosphatase gene homologue (mpgp) was found in the genome of m. burtonii (http://www.jgi.doe.gov), but an mpgs gene coding for mannosyl-3-phosphoglycerate synthase (mpgs) was absent. the gene upstream of the mpgp ... | 2006 | 16428406 |
| molecular characterization of microbial populations at two sites with differing reductive dechlorination abilities. | this study compares three molecular techniques, including terminal restriction fragment length polymorphism (t-rflp), rflp analysis with clone sequencing, and quantitative pcr (q-pcr) for surveying differences in microbial communities at two contaminated field sites that exhibit dissimilar chlorinated solvent degradation activities. at the idaho national engineering and environmental laboratory (ineel), trichloroethene (tce) was completely converted to ethene during biostimulation with lactate. ... | 2006 | 16477354 |
| complete genome sequence of the dehalorespiring bacterium desulfitobacterium hafniense y51 and comparison with dehalococcoides ethenogenes 195. | desulfitobacterium strains have the ability to dechlorinate halogenated compounds under anaerobic conditions by dehalorespiration. the complete genome of the tetrachloroethene (pce)-dechlorinating strain desulfitobacterium hafniense y51 is a 5,727,534-bp circular chromosome harboring 5,060 predicted protein coding sequences. this genome contains only two reductive dehalogenase genes, a lower number than reported in most other dehalorespiring strains. more than 50 members of the dimethyl sulfoxid ... | 2006 | 16513756 |
| quantitative pcr confirms purity of strain gt, a novel trichloroethene-to-ethene-respiring dehalococcoides isolate. | a novel dehalococcoides isolate capable of metabolic trichloroethene (tce)-to-ethene reductive dechlorination was obtained from contaminated aquifer material. growth studies and 16s rrna gene-targeted analyses suggested culture purity; however, the careful quantitative analysis of dehalococcoides 16s rrna gene and chloroethene reductive dehalogenase gene (i.e., vcra, tcea, and bvca) copy numbers revealed that the culture consisted of multiple, distinct dehalococcoides organisms. subsequent trans ... | 2006 | 16517646 |
| dynamics of reductive tce dechlorination in two distinct h(2) supply scenarios and at various temperatures. | anaerobic microbial dechlorination of trichloroethene (tce) by a mixed, dehalococcoides containing culture was investigated at different temperatures (4-60 degrees c) using propionate and lactate as a slow- and fast-releasing hydrogen (h(2)) source, respectively. distinct temperature-dependent dynamics of substrate fermentation and h(2) levels could explain observed patterns of dechlorination. while varying the temperature caused changes in rate, the overall pattern of dechlorination was charact ... | 2007 | 16570228 |
| 1,1-dichloroethene as a predominant intermediate of microbial trichloroethene reduction. | a microbial culture derived from a landfill site in dover, de consistently reduced trichloroethene (tce) to ethene through 1,1-dichloroethene (dce) as a dominant intermediate in the presence of ampicillin. a constant 1,1-dce-to-cis-dce ratio of 2.4 +/- 0.3 was observed for more than two years, while trans-dce was never detected. without ampicillin, however, tce was reduced to ethene almost exclusively through cis-dce, suggesting that the culture contained at leasttwo tce-dechlorinating populatio ... | 2006 | 16570604 |
| development and characterization of stable sediment-free anaerobic bacterial enrichment cultures that dechlorinate aroclor 1260. | we have developed sediment-free anaerobic enrichment cultures that dechlorinate a broad spectrum of highly chlorinated polychlorinated biphenyls (pcbs). the cultures were developed from aroclor 1260-contaminated sediment from the housatonic river in lenox, ma. sediment slurries were primed with 2,6-dibromobiphenyl to stimulate process n dechlorination (primarily meta dechlorination), and sediment was gradually removed by successive transfers (10%) to minimal medium. the cultures grow on pyruvate ... | 2006 | 16597944 |
| quantitative pcr targeting 16s rrna and reductive dehalogenase genes simultaneously monitors multiple dehalococcoides strains. | the 16s rrna gene provides insufficient information to infer the range of chloroorganic electron acceptors used by different dehalococcoides organisms. to overcome this limitation and provide enhanced diagnostic tools for growth measurements, site assessment, and bioremediation monitoring, a quantitative real-time pcr (qpcr) approach targeting 16s rrna genes and three dehalococcoides reductive dehalogenase (rdase) genes with assigned function (i.e., tcea, bvca, and vcra) was designed and evaluat ... | 2006 | 16597981 |
| methanosarcina spp. drive vinyl chloride dechlorination via interspecies hydrogen transfer. | two highly enriched cultures containing dehalococcoides spp. were used to study the effect of aceticlastic methanogens on reductive vinyl chloride (vc) dechlorination. in terms of aceticlastic methanogens, one culture was dominated by methanosaeta, while the other culture was dominated by methanosarcina, as determined by fluorescence in situ hybridization. cultures amended with 2-bromoethanesulfonate (bes), an efficient inhibitor of methanogens, exhibited slow vc dechlorination when grown on ace ... | 2006 | 16598001 |
| anaerobic bioremediation of groundwater containing a mixture of 1,1,2,2-tetrachloroethane and chloroethenes. | this study investigated the biotransformation pathways of 1,1,2,2-tetrachloroethane (1,1,2,2-teca) in the presence of chloroethenes (i.e. tetrachloroethene, pce; trichloroethene, tce) in anaerobic microcosms constructed with subsurface soil and groundwater from a contaminated site. when amended with yeast extract, lactate, butyrate, or h2 and acetate, 1,1,2,2-teca was initially dechlorinated via both hydrogenolysis to 1,1,2-trichloroethane (1,1,2-tca) (major pathway) and dichloroelimination to d ... | 2006 | 16715399 |
| experimental evidence for a lack of thermodynamic control on hydrogen concentrations during anaerobic degradation of chlorinated ethenes. | hydrogen (h2) concentrations during reductive dechlorination of cis-dichloroethene (cdce) and vinyl chloride (vc) were investigated with respectto the influence of parameters entering the gibbs free energy expression of the reactions. a series of laboratory experiments was conducted employing a mixed, dehalococcoides-containing enrichment culture capable of complete dechlorination of chlorinated ethenes. the objective was to investigate whether a constant energy gain controls h2 levels in dechlo ... | 2006 | 16786686 |
| biological enhancement of tetrachloroethene dissolution and associated microbial community changes. | a bench-scale study was performed to evaluate the enhancement of tetrachloroethene (pce) dissolution from a dense nonaqueous phase liquid (dnapl) source zone due to reductive dechlorination. the study was conducted in a pair of two-dimensional bench-scale aquifer systems using soil and groundwater from dover air force base, de. after establishment of pce source zones in each aquifer system, one was biostimulated (addition of electron donor) while the other was biostimulated and then bioaugmented ... | 2006 | 16786703 |
| the effect of varying levels of sodium bicarbonate on polychlorinated biphenyl dechlorination in hudson river sediment cultures. | the addition of different concentrations of sodium bicarbonate had a profound effect on 2,3,4,5-chlorobiphenyl (2,3,4,5-cb) dechlorination in hudson river sediment cultures. the most extensive dechlorination was observed in cultures to which 100 mg l(-1) bicarbonate was added. cultures amended with 1000 mg l(-1) bicarbonate had the least extensive dechlorination, with 2,4-cb and 2,5-cb as predominant end-products. a significant loss of total chlorinated biphenyl mass was observed in cultures to ... | 2006 | 16817937 |
| temporal expression of respiratory genes in an enrichment culture containing dehalococcoides ethenogenes. | multiple reductive dehalogenase (rdase), hydrogenase (h2ase), and other respiration-associated (ra) oxidoreductase genes have been identified in cultured representatives of dehalococcoides. although their products are likely to play key roles in the environmentally important process of reductive dechlorination, very little information is available about their regulation and specific functions. here we show increased expression and temporal variability in the expression of five rdase genes and in ... | 2006 | 16885302 |
| relationship between dehalococcoides dna in ground water and rates of reductive dechlorination at field scale. | certain strains of dehalococcoides bacteria can dechlorinate chlorinated ethylenes to harmless products. this study was conducted to determine if there is a valid association between the density of dehalococcoides dna in ground water and the observed rates of reductive dechlorination at field scale. dehalococcoides dna in water from monitoring wells was determined using the quantitative real time polymerase chain reaction (q-pcr) with dna primer set specific for dehalococcoides organisms. dechlo ... | 2006 | 16889813 |
| microbial reductive debromination of polybrominated diphenyl ethers (pbdes). | polybrominated diphenyl ethers (pbdes) are a class of widely used flame retardants that have recently been detected in environmental samples, diverse biota, human blood serum, and breast milk at exponentially increasing concentrations. currently, little is known about the fate of these compounds, and in particular, about the microbial potential to degrade them. in this study, debromination of deca-bde and an octa-bde mixture is demonstrated with anaerobic bacteria including sulfurospirillum mult ... | 2006 | 16903281 |
| a modeling study and implications of competition between dehalococcoides ethenogenes and other tetrachloroethene-respiring bacteria. | bioaugmentation with cultures containing dehalococcoides strains that dechlorinate cis-1,2-dichloroethene (cdce) to ethene is often recommended at sites where indigenous populations dechlorinate tetrachloroethene (pce) to cdce. in these cases, dehalococcoides populations may have to compete with other dehalorespirers for chlorinated ethenes and/or electron donors. a continuous-flow stirred tank reactor model was used to describe the substrate interactions in three conceptual models of competitio ... | 2006 | 16903288 |
| transcription and mass-spectroscopic proteomic studies of electron transport oxidoreductases in dehalococcoides ethenogenes. | besides 19 potential reductive dehalogenase genes, the genome of dehalococcoides ethenogenes strain 195 contains over 60 genes annotated as encoding oxidoreductases, including five hydrogenase complexes and a formate dehydrogenase (fdh). using quantitative reverse transcriptase polymerase chain reaction, we found that genes encoding a periplasmic hup hydrogenase and the fdh were the most highly expressed in batch-grown pure cultures, in which the h2 partial pressure was >0.1 atm, and in butyrate ... | 2006 | 16913910 |
| discrimination of multiple dehalococcoides strains in a trichloroethene enrichment by quantification of their reductive dehalogenase genes. | while many anaerobic microbial communities are capable of reductively dechlorinating tetrachloroethene (pce) and trichloroethene (tce) to dichloroethene (dce), vinyl chloride (vc), and finally ethene, the accumulation of the highly toxic intermediates, cis-dce (cdce) and vc, presents a challenge for bioremediation processes. members of the genus dehalococcoides are apparently solely responsible for dechlorination beyond dce, but isolates of dehalococcoides each metabolize only a subset of pce de ... | 2006 | 16957207 |
| reductive dehalogenase gene expression as a biomarker for physiological activity of dehalococcoides spp. | this study characterizes the transcriptional expression of the reductive dehalogenase (rdase)-encoding tcea and vcra genes and evaluates their applicability as potential biological markers of dehalococcoides activity. when dehalococcoides ethenogenes 195 was provided with trichloroethene (tce) as the electron acceptor, the expression of the tcea gene increased by 90-fold relative to that in cells starved of chlorinated ethenes, demonstrating that tcea gene expression is indicative of the active ... | 2006 | 16957242 |
| bacterial diversity of an acidic louisiana groundwater contaminated by dense nonaqueous-phase liquid containing chloroethanes and other solvents. | bacterial concentration and diversity was assessed in a moderately acidic (ph 5.1) anaerobic groundwater contaminated by chlorosolvent-containing dnapl at a superfund site located near baton rouge, louisiana. groundwater analysis revealed a total aqueous-phase chlorosolvent concentration exceeding 1000 mg l(-1), including chloroethanes, vinyl chloride, 1,2-dichloropropane, and hexachloro-1,3-butadiene as the primary contaminants. direct counting of stained cells revealed more than 3 x 10(7) cell ... | 2006 | 16958913 |
| comparative proteomics of dehalococcoides spp. reveals strain-specific peptides associated with activity. | anaerobic reductive dehalogenation by dehalococcoides spp. is an ideal system for studying functional diversity of closely related strains of bacteria. in dehalococcoides spp., reductive dehalogenases (rdases) are key respiratory enzymes involved in the anaerobic detoxification of halogenated compounds at contaminated sites globally. although housekeeping genes sequenced from dehalococcoides spp. are >85% identical at the amino acid level, different strains are capable of dehalogenating diverse ... | 2007 | 17098919 |
| relevance of side reactions in anaerobic reductive dechlorination microcosms amended with different electron donors. | in this study we examined the relative importance of side reactions, i.e. the formation of volatile fatty acids (vfa), and the reduction of alternative electron acceptors (nitrate, sulfate, fe(iii)), in enhanced dechlorination microcosms, amended with different electron donors, namely lactate, butyrate, and h(2)+acetate mixture. dechlorination reactions proceeded at low rates and consequently, nearly all of the reducing equivalents (over 99%) available from electron donor consumption were channe ... | 2007 | 17107702 |
| microbial composition of chlorinated ethene-degrading cultures dominated by dehalococcoides. | the community composition of microbial cultures degrading tetrachloroethene (pce), trichloroethene (tce), cis-1,2-dichloroethene (cdce) and vinyl chloride (vc) to ethene was studied. a combination of pcr-denaturing gradient gel electrophoresis (pcr-dgge) and 16s rrna gene sequence analysis revealed that all cultures contained dehalococcoides populations, but that the populations of other organisms varied widely. based on the sequences of cloned 16s rrna genes, real-time pcr methods were develope ... | 2006 | 17117995 |
| assessment of the natural attenuation of chlorinated ethenes in an anaerobic contaminated aquifer in the bitterfeld/wolfen area using stable isotope techniques, microcosm studies and molecular biomarkers. | the in situ degradation of chlorinated ethenes was assessed in an anaerobic aquifer using stable isotope fractionation approaches, microcosm studies and taxon specific detection of specific dehalogenating groups of bacteria. the aquifer in the bitterfeld/wolfen region in germany contained all chlorinated ethenes, benzene and toluene as contaminants. the concentrations and isotope composition of the chlorinated ethenes indicated biodegradation of the contaminants. microcosm studies confirmed the ... | 2007 | 17123579 |
| temperature dependence of anaerobic tce-dechlorination in a highly enriched dehalococcoides-containing culture. | temperature dependence of reductive trichloroethene (tce) dechlorination was investigated in an enrichment culture (kb-1), using lactate or propionate as electron donors at a temperature interval from 4 to 60 degrees c. dechlorination was complete to ethene at temperatures between 10 and 30 degrees c (lactate-amended) and between 15 and 30 degrees c (propionate-amended). dechlorination stalled at cis-1,2-dichloroethene (cdce) at 4 degrees c (lactate-amended), at and below 10 degrees c (propionat ... | 2007 | 17129596 |
| dechlorination after thermal treatment of a tce-contaminated aquifer: laboratory experiments. | a microcosm study was conducted to evaluate dechlorination of trichloroethene (tce) to ethene and survival of dechlorinating bacteria after a thermal treatment in order to explore the potential for post-thermal bioremediation. unamended microcosms containing groundwater and aquifer material from a contaminated site dechlorinated tce to cis-1,2-dichloroethene (cdce), while lactate-amended microcosms dechlorinated tce to cdce or ethene. a thermal treatment was simulated by heating a sub-set of mic ... | 2007 | 17174379 |
| environmental distribution of the trichloroethene reductive dehalogenase gene (tcea) suggests lateral gene transfer among dehalococcoides. | the trichloroethene reductive dehalogenase gene (tcea) of dehalococcoides spp. was detected in 12 of 21 trichloroethene-to-ethene dechlorinating enrichment cultures established from aquifer and sediment samples collected from diverse geographic locations in the usa. analysis of the tcea chromosomal regions indicated that the tcea genes shared greater than 95% sequence identity, and all shared identical tceab spacer sequences and tceb genes downstream of tcea. a putative transposable element (pte ... | 2007 | 17233752 |
| the dehalococcoides population in sediment-free mixed cultures metabolically dechlorinates the commercial polychlorinated biphenyl mixture aroclor 1260. | microbial reductive dechlorination of commercial polychlorinated biphenyl (pcb) mixtures (e.g., aroclors) in aquatic sediments is crucial to achieve detoxification. despite extensive efforts over nearly two decades, the microorganisms responsible for aroclor dechlorination remained elusive. here we demonstrate that anaerobic bacteria of the dehalococcoides group derived from sediment of the housatonic river (lenox, ma) simultaneously dechlorinate 64 pcb congeners carrying four to nine chlorines ... | 2007 | 17308182 |
| unusual codon bias in vinyl chloride reductase genes of dehalococcoides species. | vinyl chloride reductases (vc-rdase) are the key enzymes for complete microbial reductive dehalogenation of chloroethenes, including the groundwater pollutants tetrachloroethene and trichloroethene. analysis of the codon usage of the vc-rdase genes vcra and bvca showed that these genes are highly unusual and are characterized by a low g+c fraction at the third position. the third position of codons in vc-rdase genes is biased toward the nucleotide t, even though available dehalococcoides genome ... | 2007 | 17308190 |
| influence of vitamin b12 and cocultures on the growth of dehalococcoides isolates in defined medium. | bacteria belonging to the genus dehalococcoides play a key role in the complete detoxification of chloroethenes as these organisms are the only microbes known to be capable of dechlorination beyond dichloroethenes to vinyl chloride (vc) and ethene. however, dehalococcoides strains usually grow slowly with a doubling time of 1 to 2 days and have complex nutritional requirements. here we describe the growth of dehalococcoides ethenogenes 195 in a defined mineral salts medium, improved growth of st ... | 2007 | 17337553 |
| microbial reductive dechlorination of aroclor 1260 in baltimore harbor sediment microcosms is catalyzed by three phylotypes within the phylum chloroflexi. | the specific dechlorination pathways for aroclor 1260 were determined in baltimore harbor sediment microcosms developed with the 11 most predominant congeners from this commercial mixture and their resulting dechlorination intermediates. most of the polychlorinated biphenyl (pcb) congeners were dechlorinated in the meta position, and the major products were tetrachlorobiphenyls with unflanked chlorines. using pcr primers specific for the 16s rrna genes of known pcb-dehalogenating bacteria, we de ... | 2007 | 17351091 |