Project description:The genomes of three newly isolated Dehalococcoides strains (11a, 11a5 and MB) were compared against known genomes in the Dehalococcoides genus via a microarray targeting four sequenced Dehalococcoides strains (195, CBDB1, BAV1, and VS). All three strains exhibit different dechlorination patterns, with strains 11a dechlorinating TCE to ethene, 11a5 dechlorinating TCE to VC and MB dechlorinating PCE only to isomers of DCE. Hybridization of their respective genomic DNA to the microarrays showed that the genomes of strains 11a and 11a5 show great similarity to each other and to strains CBDB1 and BAV1 of the Pinellas subgroup, while strain MB shows strong genome similarity to members of the Cornell subgroup. All genes within the respective subgroups that were not detected by microarray are within the respective high plasticity regions or integrated elements of the sequenced strains. A large number of reductive dehalogenase (RDase)-encoding genes are present within each genome, and the presence of the vcrA and tceA genes in strains 11a and 11a5 respectively, and the absence of any of the four functionally-characterized chlorinated ethene RDases (pceA, tceA, vcrA, bvcA) within strain MB appear to dictate chlorinated ethene usages regardless of the respective core genome phylogeny of the three strains. Considering the current data set together with previous comparative genomics results from application of the Dehalococcoides genus microarray to two other un-sequenced strains, the observed incongruence between the core genome phylogeny and chlorinated ethene usage of Dehalococcoides strains is likely driven by horizontal gene transfer of functional RDases. The other genomic features that are repeatedly observed in the microarray analyses of all five un-sequenced Dehalococcoides strains as well as the environmental implications on this work are presented in this study. The genomic DNA (gDNA) of each culture was analyzed in triplicate. gDNA from the two newly isolated Dehalococcoides strains 11a and 11a5 were analyzed.
Project description:Four stable and robust TCE-dechlorinating microbial communities were enriched from TCE-contaminated groundwater under four different conditions exploring two parameters, high and low methanogenic activity (Meth and NoMeth), with and without vitamin B12 supplement (MethB12 and NoMethB12, Meth and NoMeth, respectively). Identical amounts of lactate (2.7 mmol) and TCE (20 M-NM-<l) were supplied as electron donor and electron acceptor. All four cultures were capable of reductively dechlorinating TCE to VC and ethene. Genomic DNA of the four enrichments was applied on a quad-Dhc-genome microarray in order to characterize the gene content of Dehalococcoides species present in the four enrichments The genomic DNA of four enrichment cultures completely dechlorinated TCE to VC and ethene was used on the microarray to query Dehalococcoides species present in the mixed cultures.
Project description:Four stable and robust TCE-dechlorinating microbial communities were enriched from TCE-contaminated groundwater under four different conditions exploring two parameters, high and low methanogenic activity (Meth and NoMeth), with and without vitamin B12 supplement (MethB12 and NoMethB12, Meth and NoMeth, respectively). Identical amounts of lactate (2.7 mmol) and TCE (20 μl) were supplied as electron donor and electron acceptor. All four cultures were capable of reductively dechlorinating TCE to VC and ethene. Genomic DNA of the four enrichments was applied on a quad-Dhc-genome microarray in order to characterize the gene content of Dehalococcoides species present in the four enrichments
Project description:Tetrachloroethene (PCE) and trichloroethene (TCE) are prevalent groundwater contaminants that can be completely reductively dehalogenated by Dehalococcoides organisms. A Dehalococcoides-containing microbial consortium (ANAS) with the ability to degrade TCE to ethene, an innocuous end-product, was previously enriched from contaminated soil. A whole-genome photolithographic microarray was developed based on the genome of Dehalococcoides ethenogenes 195 (strain 195). This microarray contains probes designed to hybridize to >99% of the predicted protein-coding sequences in the strain 195 genome. DNA from ANAS was hybridized to the microarray to characterize the genomic content of the ANAS enrichment. The microarray revealed that the genes associated with central metabolism including an apparently incomplete carbon fixation pathway, cobalamin salvaging system, nitrogen fixation pathway, and five hydrogenase complexes are present in both strain 195 and ANAS. Although the gene encoding the TCE reductase tceA was detected, 13 of the 19 reductive dehalogenase genes present in strain 195 were not detected in ANAS. Additionally, 88% of the genes in predicted integrated genetic elements in strain 195 were not detected in ANAS, consistent with these elements being genetically mobile. Sections of the tryptophan operon and an operon encoding an ABC transporter in strain 195 were also not detected in ANAS. These insights into the diversity of Dehalococcoides genomes will improve our understanding of the physiology and evolution of these bacteria which is essential in developing effective strategies for bioremediation of PCE and TCE in the environment. Keywords: comparative genomic hybridization Genomic DNA from each culture was divided into replicate samples which were independently fragmented, labeled, and hybridized to arrays. Two microarrays were processed for the positive control (strain 195), two for the negative control (D. restrictus), and five for the ANAS enrichment culture(two analyses from one biological sample followed one year later by three analyses of a second biological sample).
Project description:Tetrachloroethene (PCE) and trichloroethene (TCE) are prevalent groundwater contaminants that can be completely reductively dehalogenated by Dehalococcoides organisms. A Dehalococcoides-containing microbial consortium (ANAS) with the ability to degrade TCE to ethene, an innocuous end-product, was previously enriched from contaminated soil. A whole-genome photolithographic microarray was developed based on the genome of Dehalococcoides ethenogenes 195 (strain 195). This microarray contains probes designed to hybridize to >99% of the predicted protein-coding sequences in the strain 195 genome. DNA from ANAS was hybridized to the microarray to characterize the genomic content of the ANAS enrichment. The microarray revealed that the genes associated with central metabolism including an apparently incomplete carbon fixation pathway, cobalamin salvaging system, nitrogen fixation pathway, and five hydrogenase complexes are present in both strain 195 and ANAS. Although the gene encoding the TCE reductase tceA was detected, 13 of the 19 reductive dehalogenase genes present in strain 195 were not detected in ANAS. Additionally, 88% of the genes in predicted integrated genetic elements in strain 195 were not detected in ANAS, consistent with these elements being genetically mobile. Sections of the tryptophan operon and an operon encoding an ABC transporter in strain 195 were also not detected in ANAS. These insights into the diversity of Dehalococcoides genomes will improve our understanding of the physiology and evolution of these bacteria which is essential in developing effective strategies for bioremediation of PCE and TCE in the environment. Keywords: comparative genomic hybridization
Project description:Polybrominated diphenyl ethers (PBDEs) are persistent, highly toxic, and widely distributed environmental pollutants. The microbial populations and functional reductive dehalogenases (RDases) responsible for PBDEs debromination in anoxic systems remain poorly understood, which confounds bioremediation of PBDE-contaminated sites. Here we report a PBDE-debrominating enrichment culture dominated by a previously undescribed Dehalococcoides mccartyi population. A D. mccartyi strain, designated TZ50, whose genome contains 25 putative RDase encoding genes was isolated from the debrominating enrichment culture. Strain TZ50 dehalogenated a mixture of penta- and tetra-BDE congeners (total BDEs 1.48 uM) to diphenyl ether within two weeks (0.58 uM Br- /d) via ortho- and meta- bromine elimination; strain TZ50 also dechlorinated tetrachloroethene (PCE) to vinyl chloride and ethene (260.2 M Cl- /d). Native-PAGE, proteomic profiling, and in vitro enzymatic activity assays implicated the involvement of three RDases in PBDEs and PCE dehalogenation. Two RDases, TZ50_0172 (PteATZ50) and TZ50_1083 (TceATZ50), were responsible for debromination of penta- and tetra-BDEs to di-BDE. TZ50_0172 and TZ50_1083 were also implicated in dechlorination of PCE to TCE and of TCE to vinyl chloride/ethene, respectively. The other expressed dehalogenase, TZ50_0090, was associated with debromination of di-BDE to diphenyl ether, but its role in PCE dechlorination was unclear. Comparatively few RDases are known to be involved in PBDE debromination and the identification of PteATZ50, TceATZ50, and TZ50_0090 provides additional information for evaluating debromination potential at contaminated sites. Moreover, the bifunctionality of the PteATZ50 and TceATZ50 in both PBDEs and PCE dehalogenation makes strain TZ50 a suitable candidate for remediation of co-contaminated sites.
Project description:The aim of this study is to obtain a systems level understanding of the interactions between Dehalococcoides and corrinoid-supplying microorganisms by analyzing community structures and functional compositions, activities and dynamics in trichloroethene (TCE)-dechlorinating enrichments. Metagenomes and metatranscriptomes of the dechlorinating enrichments with and without exogenous cobalamin were compared. Seven draft genomes were binned from the metagenomes. At an early stage (2 d), more transcripts of genes in the Veillonellaceae bin-genome were detected in the metatranscriptome of the enrichment with exogenous cobalamin compared to the one without cobalamin addition. Among these genes, sporulation-related genes exhibited the highest differential expression when cobalamin was not added, suggesting a possible release route of corrinoids from corrinoid-producers. Other differentially expressed genes include those involved in energy conservation and nutrient transport (including cobalt transport). The most highly expressed corrinoid de novo biosynthesis pathway was also assigned to the Veillonellaceae bin-genome. Targeted qPCR analyses confirmed higher transcript abundances of those corrinoid biosynthesis genes in the enrichment without exogenous cobalamin. Furthermore, Dehalococcoides' corrinoid salvaging and modification pathway was upregulated in response to the cobalamin stress. This study provides important insights into the microbial interactions and roles of members of dechlorinating communities under cobalamin-limited conditions.