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:Groundwater salinization threatens contaminant bioremediation worldwide, yet how syntrophic microbial consortia—central to these processes—respond to salinity stress remains poorly understood. Using a defined trichloroethene-dechlorinating consortium comprising Dehalococcoides mccartyi strain 195 (Dhc195), Desulfovibrio vulgaris Hildenborough (DvH), and Pelosinus fermentans R7 (PfR7), we show that functional resilience under salinity is governed by syntrophic dependencies rather than the tolerance of keystone organisms alone. Under chronic salinity, dechlorination became incomplete above 16 g/L NaCl despite stable Dhc195 and DvH, reflecting impaired vitamin B12 supply by PfR7. Co-amendment with glycine betaine and vitamin B12 sustained function under chronic moderate salinity up to ~18 g/L NaCl, but not during acute salinity upsurge greater than 21 g/L NaCl. Axenic cultures showed uncoupling of Dhc195 growth and dechlorination at high salinity, while transcriptomic analyses indicated a shift toward survival-oriented, amino acid–based adaptation during acute stress. Consortium metabolomics further highlighted membrane remodeling and altered metabolic exchange under salinity stress. Together, these findings demonstrate that sustaining bioremediation in salinizing aquifers requires community-level strategies that explicitly account for syntrophic vulnerability rather than organism-centric tolerance.
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 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.