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.
Project description:Organohalide-respiring Dehalococcoidia bacteria are one of the few microorganisms capable of transforming chlorinated solvents to benign ethene in anoxic environments. The tceA gene found in these bacteria, coding the trichloroethene-dechlorinating RDase TceA, is frequently detected in contaminated groundwater but not recognized as a biomarker for vinyl chloride detoxification. Here, we demonstrate that the tceA-carrying Dehalococcoides mccartyi (Dhc) strains FL2 and 195 grow with VC as electron acceptor when sufficient vitamin B12 is provided. Global proteomic profiling confirmed the predominant TceA expression in VC-grown Dhc FL2 cells, providing a line of evidence for the implication of TceA in respiratory VC reductive dechlorination.
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:The proteome of the anaerobic bacterium Dehalococcoides mccartyi strain CBDB1 from the phylum Chloroflexi was investigated. D. mccartyi strain CBDB1 is a model organism for organohalide respiration where halogenated organic compounds serve as terminal electron acceptors. A wide range of halogenated organic compounds have been shown to be dehalogenated by the strain CBDB1. Therefore, D. mccartyi strain CBDB1 is a promising candidate for bioremediation application. Proteomic analysis of cultures grown with hexachlorobenzene as only electron acceptor resulted in identification of 8,491 distinct peptides which represents 1,023 proteins. A coverage of 70% of the 1,458 annotated proteins for strain CBDB1 was achieved. In addition, a spectral library was created from the annotated spectra. By using proteogenomics, 18 previously not annotated peptides were identified which contribute to four proteins previously not annotated and corrections in length of eight protein coding sequences.