scholarly journals Metagenomic- and Cultivation-Based Exploration of Anaerobic Chloroform Biotransformation in Hypersaline Sediments as Natural Source of Chloromethanes

2020 ◽  
Vol 8 (5) ◽  
pp. 665
Author(s):  
Peng Peng ◽  
Yue Lu ◽  
Tom N.P. Bosma ◽  
Ivonne Nijenhuis ◽  
Bart Nijsse ◽  
...  
Keyword(s):  
Vitamin B12 ◽  
Reductive Dechlorination ◽  
Electron Donors ◽  
Natural Source ◽  
Hypersaline Lake ◽  
Reductive Dehalogenase ◽  
Enrichment Cultures ◽  
Cobalamin Biosynthesis ◽  
Abiotic Control ◽  
Hypersaline Sediments

Chloroform (CF) is an environmental contaminant that can be naturally formed in various environments ranging from forest soils to salt lakes. Here we investigated CF removal potential in sediments obtained from hypersaline lakes in Western Australia. Reductive dechlorination of CF to dichloromethane (DCM) was observed in enrichment cultures derived from sediments of Lake Strawbridge, which has been reported as a natural source of CF. No CF removal was observed in abiotic control cultures without artificial electron donors, indicating biotic CF dechlorination in the enrichment cultures. Increasing vitamin B12 concentration from 0.04 to 4 µM in enrichment cultures enhanced CF removal and reduced DCM formation. In cultures amended with 4 µM vitamin B12 and 13C labelled CF, formation of 13CO2 was detected. Known organohalide-respiring bacteria and reductive dehalogenase genes were neither detected using quantitative PCR nor metagenomic analysis of the enrichment cultures. Rather, members of the order Clostridiales, known to co-metabolically transform CF to DCM and CO2, were detected. Accordingly, metagenome-assembled genomes of Clostridiales encoded enzymatic repertoires for the Wood-Ljungdahl pathway and cobalamin biosynthesis, which are known to be involved in fortuitous and nonspecific CF transformation. This study indicates that hypersaline lake microbiomes may act as a filter to reduce CF emission to the atmosphere.

scholarly journals Metagenomic- and cultivation-based exploration of anaerobic chloroform biotransformation in hypersaline sediments as natural source of chloromethanes

2019 ◽  
Author(s):  
Peng Peng ◽  
Yue Lu ◽  
Tom N.P. Bosma ◽  
Ivonne Nijenhuis ◽  
Bart Nijsse ◽  
...  
Keyword(s):  
Salt Lake ◽  
Extreme Environments ◽  
Natural Source ◽  
Hypersaline Lake ◽  
Stable Isotope Labelling ◽  
Hypersaline Lakes ◽  
Metagenome Analysis ◽  
Reductive Dehalogenase ◽  
Enrichment Cultures ◽  
Interdisciplinary Approaches

AbstractChloroform (CF) is an environmental contaminant that can be naturally formed in various environments ranging from forest soils to salt lakes. Here we investigated CF removal potential in sediments obtained from hypersaline lakes in Western Australia. Reductive dechlorination of CF to dichloromethane (DCM) was observed in enrichment cultures derived from sediments of Lake Strawbridge, which has been reported as a natural source of CF. The lack of CF removal in the abiotic control cultures without artificial electron donors indicated that the observed CF removal is a biotic process. Metabolite analysis with 13C labelled CF in the sediment-free enrichment cultures (pH 8.5, salinity 5%) revealed that increasing the vitamin B12 concentration from 0.04 to 4 μM enhanced CF removal, reduced DCM formation, and increased 13CO2 production, which is likely a product of CF oxidation. Known organohalide-respiring bacteria and reductive dehalogenase genes were neither detected by quantitative PCR nor metagenomic analysis. Rather, members of the order Clostridiales, known to co-metabolically transform CF to DCM and CO2, were detected in the enrichment cultures. Genome-resolved metagenome analysis indicated that their genomes encode enzymatic repertoires for the Wood-Ljungdahl pathway and cobalamin biosynthesis that are known to be involved in co-metabolic CF transformation.ImportanceMore than 90% of the global CF emission to the atmosphere originates from natural sources, including saline environments such as salt lake sediments. However, knowledge about the microbial metabolism of CF in such extreme environments is lacking. Here we showed CF transformation potential in a hypersaline lake that was reported as a natural source of CF production. Application of interdisciplinary approaches of microbial cultivation, stable isotope labelling, and metagenomics aided in defining potential chloroform transformation pathways. This study indicates that microbiota may act as a filter to reduce CF emission from hypersaline lakes to the atmosphere, and expands our knowledge of halogen cycling in extreme hypersaline environments.

scholarly journals A Microcosm Treatability Study for Evaluating Wood Mulch-Based Amendments as Electron Donors for Trichloroethene (TCE) Reductive Dechlorination

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1949
Author(s):  
Edoardo Masut ◽  
Alessandro Battaglia ◽  
Luca Ferioli ◽  
Anna Legnani ◽  
Carolina Cruz Viggi ◽  
...  
Keyword(s):  
Electron Donor ◽  
Environmental Sustainability ◽  
Reductive Dechlorination ◽  
Environmental Remediation ◽  
Low Cost ◽  
Chlorinated Solvents ◽  
Electron Donors ◽  
Chlorinated Ethenes ◽  
Dehalococcoides Mccartyi ◽  
Wood Mulch

In this study, wood mulch-based amendments were tested in a bench-scale microcosm experiment in order to assess the treatability of saturated soils and groundwater from an industrial site contaminated by chlorinated ethenes. Wood mulch was tested alone as the only electron donor in order to assess its potential for stimulating the biological reductive dechlorination. It was also tested in combination with millimetric iron filings in order to assess the ability of the additive to accelerate/improve the bioremediation process. The efficacy of the selected amendments was compared with that of unamended control microcosms. The results demonstrated that wood mulch is an effective natural and low-cost electron donor to stimulate the complete reductive dechlorination of chlorinated solvents to ethene. Being a side-product of the wood industry, mulch can be used in environmental remediation, an approach which perfectly fits the principles of circular economy and addresses the compelling needs of a sustainable and low environmental impact remediation. The efficacy of mulch was further improved by the co-presence of iron filings, which accelerated the conversion of vinyl chloride into the ethene by increasing the H2 availability rather than by catalyzing the direct abiotic dechlorination of contaminants. Chemical analyses were corroborated by biomolecular assays, which confirmed the stimulatory effect of the selected amendments on the abundance of Dehalococcoides mccartyi and related reductive dehalogenase genes. Overall, this paper further highlights the application potential and environmental sustainability of wood mulch-based amendments as low-cost electron donors for the biological treatment of chlorinated ethenes.

Enrichment and isolation of a reductively debrominating bacterium from the burrow of a bromometabolite-producing marine hemichordate

1995 ◽  
Vol 41 (7) ◽  
pp. 637-642 ◽  
Author(s):  
Charles C. Steward ◽  
Terry C. Dixon ◽  
Yung Pin Chen ◽  
Charles R. Lovell
Keyword(s):  
Electron Donors ◽  
Ortho Position ◽  
Enrichment Cultures ◽  
Bacterium Strain

An anaerobic 2,4,6-tribromophenol debrominating bacterium, strain DSL-1, was isolated from enrichment cultures inoculated with sediment from the burrows of the bromoaromatic-producing marine hemichordates Balanoglossus aurantiacus and Saccoglossus kowalewskyi. DSL-1 preferentially removed ortho-position bromines, resulting in the transient appearance of 2,4-dibromophenol and accumulation of 4-bromophenol. Cell-free extracts and partially purified reductive debrominase preparations from DSL-1 also debrominated 2,4,6-tribromophenol, yielding 2,4-dibromophenol and 4-bromophenol. Both NADH and NADPH stimulated 2,4,6-tribromophenol reduction by partially purified debrominase. These data are consistent with a reductive debromination mechanism. The organic cosubstrate(s) and specific electron donors used by DSL-1 in vivo are currently unknown.Key words: dehalogenation, bromometabolites, bromophenols, hemichordates.

scholarly journals Evaluation of the Bioelectrochemical Approach and Different Electron Donors for Biological Trichloroethylene Reductive Dichlorination

Toxics ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 37
Author(s):  
Edoardo Dell’Armi ◽  
Marta Maria Rossi ◽  
Lucia Taverna ◽  
Marco Petrangeli Papini ◽  
Marco Zeppilli
Keyword(s):  
Reductive Dechlorination ◽  
Molecular Hydrogen ◽  
Batch Reactor ◽  
Electron Donors ◽  
Utilization Efficiency ◽  
Batch Reactors ◽  
Organic Substrates ◽  
Chlorinated Aliphatic Hydrocarbons ◽  
Low Solubility ◽  
Dechlorination Reaction

Trichloroethylene (TCE) and more in general chlorinated aliphatic hydrocarbons (CAHs) can be removed from a contaminated matrix thanks to microorganisms able to perform the reductive dechlorination reaction (RD). Due to the lack of electron donors in the contaminated matrix, CAHs’ reductive dechlorination can be stimulated by fermentable organic substrates, which slowly release molecular hydrogen through their fermentation. In this paper, three different electron donors constituted by lactate, hydrogen, and a biocathode of a bioelectrochemical cell have been studied in TCE dechlorination batch experiments. The batch reactors evaluated in terms of reductive dechlorination rate and utilization efficiency of the electron donor reported that the bio-electrochemical system (BES) showed a lower RD rate with respect of lactate reactor (51 ± 9 µeq/d compared to 98 ± 4 µeq/d), while the direct utilization of molecular hydrogen gave a significantly lower RD rate (19 ± 8 µeq/d), due to hydrogen low solubility in liquid media. The study also gives a comparative evaluation of the different electron donors showing the capability of the bioelectrochemical system to reach comparable efficiencies with a fermentable substrate without the use of other chemicals, 10.7 ± 3.3% for BES with respect of 3.5 ± 0.2% for the lactate-fed batch reactor. This study shows the BES capability of being an alternative at classic remediation approaches.

Kinetics of tetrachloroethylene-reductive dechlorination catalyzed by vitamin B12

1998 ◽  
Vol 17 (9) ◽  
pp. 1681-1688 ◽  
Author(s):  
David R. Burris ◽  
Carrie A. Delcomyn ◽  
Baolin Deng ◽  
Leslie E. Buck ◽  
Kirk Hatfield
Keyword(s):  
Vitamin B12 ◽  
Reductive Dechlorination ◽  
Kinetics Of

scholarly journals Unexpected Specificity of Interspecies Cobamide Transfer from Geobacter spp. to Organohalide-Respiring Dehalococcoides mccartyi Strains

2012 ◽  
Vol 78 (18) ◽  
pp. 6630-6636 ◽  
Author(s):  
Jun Yan ◽  
Kirsti M. Ritalahti ◽  
Darlene D. Wagner ◽  
Frank E. Löffler
Keyword(s):  
Reductive Dechlorination ◽  
De Novo ◽  
Synthetic Medium ◽  
Geobacter Sulfurreducens ◽  
Rrna Gene ◽  
Content Type ◽  
Reductive Dehalogenase ◽  
Dehalococcoides Mccartyi ◽  
Gene Copies ◽  
Pure Cultures

ABSTRACTDehalococcoides mccartyistrains conserve energy from reductive dechlorination reactions catalyzed by corrinoid-dependent reductive dehalogenase enzyme systems.Dehalococcoideslacks the ability forde novocorrinoid synthesis, and pure cultures require the addition of cyanocobalamin (vitamin B12) for growth. In contrast,Geobacter lovleyi, which dechlorinates tetrachloroethene tocis-1,2-dichloroethene (cis-DCE), and the nondechlorinating speciesGeobacter sulfurreducenshave complete sets of cobamide biosynthesis genes and produced 12.9 ± 2.4 and 24.2 ± 5.8 ng of extracellular cobamide per liter of culture suspension, respectively, during growth with acetate and fumarate in a completely synthetic medium.G. lovleyi-D. mccartyistrain BAV1 or strain FL2 cocultures provided evidence for interspecies corrinoid transfer, andcis-DCE was dechlorinated to vinyl chloride and ethene concomitant withDehalococcoidesgrowth. In contrast, negligible increase inDehalococcoides16S rRNA gene copies and insignificant dechlorination occurred inG. sulfurreducens-D. mccartyistrain BAV1 or strain FL2 cocultures. Apparently,G. lovleyiproduces a cobamide that complementsDehalococcoides' nutritional requirements, whereasG. sulfurreducensdoes not. Interestingly,Dehalococcoidesdechlorination activity and growth could be restored inG. sulfurreducens-Dehalococcoidescocultures by adding 10 μM 5′,6′-dimethylbenzimidazole. Observations made with theG. sulfurreducens-Dehalococcoidescocultures suggest that the exchange of the lower ligand generated a cobalamin, which supportedDehalococcoidesactivity. These findings have implications forin situbioremediation and suggest that the corrinoid metabolism ofDehalococcoidesmust be understood to faithfully predict, and possibly enhance, reductive dechlorination activities.

Aerobic synthesis of vitamin B12: ring contraction and cobalt chelation

2005 ◽  
Vol 33 (4) ◽  
pp. 815-819 ◽  
Author(s):  
D. Heldt ◽  
A.D. Lawrence ◽  
M. Lindenmeyer ◽  
E. Deery ◽  
P. Heathcote ◽  
...  
Keyword(s):  
Vitamin B12 ◽  
Metal Ion ◽  
Biosynthetic Pathway ◽  
Rhodobacter Capsulatus ◽  
Chlorophyll Synthesis ◽  
Subsequent Reduction ◽  
Ring Contraction ◽  
Contraction Process ◽  
Cobalamin Biosynthesis ◽  
Haem Iron

The aerobic biosynthetic pathway for vitamin B12 (cobalamin) biosynthesis is reviewed. Particular attention is focused on the ring contraction process, whereby an integral carbon atom of the tetrapyrrole-derived macrocycle is removed. Previous work had established that this chemically demanding step is facilitated by the action of a mono-oxygenase called CobG, which generates a hydroxy lactone intermediate. This mono-oxygenase contains both a non-haem iron and an Fe-S centre, but little information is known about its mechanism. Recent work has established that in bacteria such as Rhodobacter capsulatus, CobG is substituted by an isofunctional protein called CobZ. This protein has been shown to contain flavin, haem and Fe-S centres. A mechanism is proposed to explain the function of CobZ. Another interesting aspect of the aerobic cobalamin biosynthetic pathway is cobalt insertion, which displays some similarity to the process of magnesium chelation in chlorophyll synthesis. The genetic requirements of cobalt chelation and the subsequent reduction of the metal ion are discussed.

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