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Dehalogenation

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https://www.readbyqxmd.com/read/28811148/metagenomes-from-deep-baltic-sea-sediments-reveal-how-past-and-present-environmental-conditions-determine-microbial-community-composition
#1
Ian P G Marshall, Søren M Karst, Per H Nielsen, Bo Barker Jørgensen
Microbial communities that lived near the sediment surface in the past become slowly buried and are the source of deep subsurface communities thousands of years later. We used metagenomes to analyse how the composition of buried microbial communities may change to conform to altered environmental conditions at depth. Sediment samples were collected from down to 85m below sea floor during the Integrated Ocean Drilling Program Expedition 347, "Baltic Sea Paleoenvironment". The sediments vary in age, organic carbon content, porewater salinity, and other parameters that reflect the changing Baltic environment from the last ice age and throughout the Holocene...
August 12, 2017: Marine Genomics
https://www.readbyqxmd.com/read/28810730/hydrogen-isotope-fractionation-during-biodegradation-of-1-2-dichloroethane-potential-for-pathway-identification-using-a-multi-element-c-cl-and-h-isotope-approach
#2
Jordi Palau, Orfan Shouakar-Stash, Siti Hatijah Mortan, Rong Yu, Monica Rosell, Ernest Marco-Urrea, David L Freedman, Ramon Aravena, Albert Soler, Daniel Hunkeler
Even though multi-element isotope fractionation patterns provide crucial information to identify contaminant degradation pathways in the field, those involving hydrogen are still lacking for many halogenated groundwater contaminants and degradation pathways. This study investigates for the first time hydrogen isotope fractionation during both aerobic and anaerobic biodegradation of 1,2-dichloroethane (1,2-DCA) using five microbial cultures. Transformation-associated isotope fractionation values (ε_bulk^H) were: -115 ± 18‰ (aerobic C-H bond oxidation), -34 ± 4‰ and -38 ± 4‰ (aerobic C-Cl bond cleavage via hydrolytic dehalogenation), -57 ± 3‰ and -77 ± 9‰ (anaerobic C-Cl bond cleavage via reductive dihaloelimination)...
August 16, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28809549/mesocosm-studies-on-the-efficacy-of-bioamended-activated-carbon-for-treating-pcb-impacted-sediment
#3
Rayford B Payne, Upal Ghosh, Harold Douglas May, Christopher W Marshall, Kevin R Sowers
This report describes results of a bench-scale treatability study to evaluate the efficacy of bioaugmentation with bioamended activated carbon (AC) for in-situ treatment of polychlorinated biphenyl (PCB) impacted sediments. To this end, the ability of PCB transforming microorganisms to degrade and reduce the overall concentration of PCBs in sediment was determined in 2 L recirculating mesocosms designed to simulate conditions in Abraham's Creek in Quantico, Virginia. Ten sediment mesocosms were tested for the effects of AC alone, AC with slow release electron donor (cellulose) and different concentrations and combinations of PCB dehalogenating and degrading microorganisms added as bioamendments...
August 15, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28805056/polymer-dehalogenation-enabled-fast-fabrication-of-n-s-codoped-carbon-materials-for-superior-supercapacitor-and-deionization-applications
#4
Yingna Chang, Guoxin Zhang, Biao Han, Haoyuan Li, Cejun Hu, Yingchun Pang, Zheng Chang, Xiaoming Sun
Doped carbon materials (DCM) with multiple heteroatoms hold broad interests in electrochemical catalysis and energy storage but require several steps to fabricate, which greatly hinder their practical applications. In this study, a facile strategy is developed to enable the fast fabrication of multiply doped carbon materials via room-temperature dehalogenation of polyvinyl dichloride (PVDC) promoted by KOH with the presence of different organic dopants. A N, S-codoped carbon material (NS-DCM) is demonstratively synthesized using two dopants (dimethylformamide for N doping and dimethylsulfoxide for S doping)...
August 14, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28780870/enantioselective-hydrogen-atom-transfer-discovery-of-catalytic-promiscuity-in-flavin-dependent-ene-reductases
#5
Braddock A Sandoval, Andrew J Meichan, Todd K Hyster
Flavin has long been known to function as a single electron reductant in biological settings, but this reactivity has rarely been observed with flavoproteins used in organic synthesis. Here we describe the discovery of an enantioselective radical dehalogenation pathway for α-bromoesters using flavin-dependent 'ene'-reductases. Mechanistic experiments support the role of flavin hydroquinone as a single electron reductant, flavin semiquinone as the hydrogen atom source, and the enzyme as the source of chirality...
August 11, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28777963/biochar-accelerates-microbial-reductive-debromination-of-2-2-4-4-tetrabromodiphenyl-ether-bde-47-in-anaerobic-mangrove-sediments
#6
Juan Chen, Chao Wang, Ying Pan, Shazia Shyla Farzana, Nora Fung-Yee Tam
A common congener of polybrominated diphenyl ethers, 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), is a prevalent, persistent and toxic pollutant. It could be removed by reduction debromination by microorganisms but the rate is often slow. The study hypothesized that spent mushroom substrate derived biochar amendment could accelerate the microbial reductive debromination of BDE-47 in anaerobic mangrove sediment slurries and evaluated the mechanisms behind. At the end of 20-week experiment, percentages of residual BDE-47 in slurries amended with biochar were significantly lower but debromination products were higher than those without biochar...
July 28, 2017: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/28774660/the-distribution-and-mechanism-of-iodotyrosine-deiodinase-defied-expectations
#7
REVIEW
Zuodong Sun, Qi Su, Steven E Rokita
Iodotyrosine deiodinase (IYD) is unusual for its reliance on flavin and ability to promote reductive dehalogenation under aerobic conditions. As implied by the name, this enzyme was first discovered to catalyze iodide elimination from iodotyrosine for recycling iodide during synthesis of tetra- and triiodothyronine collectively known as thyroid hormone. However, IYD likely supports many more functions and has been shown to debrominate and dechlorinate bromo- and chlorotyrosines. A specificity for halotyrosines versus halophenols is well preserved from humans to bacteria...
July 31, 2017: Archives of Biochemistry and Biophysics
https://www.readbyqxmd.com/read/28772061/on-surface-formation-of-cumulene-by-dehalogenative-homocoupling-of-alkenyl-gem-dibromides
#8
Qiang Sun, Bay Tran, Liangliang Cai, Honghong Ma, Xin Yu, Chunxue Yuan, Meike Stöhr, Wei Xu
The on-surface activation of carbon-halogen groups represents an efficient route to produce radicals for constructing various hydrocarbons and carbon nanostructures. To our knowledge, the so far employed halide precursors have only one halogen attached to a carbon atom. It is thus of particular interest to study the effect of attaching more than one halogen atom to a carbon atom to produce multiple unpaired electrons. Here, by introducing an alkenyl gem-dibromide, we have successfully fabricated cumulene products on Au(111) by dehalogenative homocoupling reactions...
August 3, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28756319/facile-preparation-of-fluffy-n-doped-carbon-modified-with-ag-nanoparticles-as-a-highly-active-and-reusable-catalyst-for-catalytic-reduction-of-nitroarenes
#9
Xueliang Cui, Hao Li, Man Yuan, Jin Yang, Dan Xu, Zhuoyong Li, Guiqin Yu, Yanmin Hou, Zhengping Dong
Novel fluffy smoke like mesoporous N-doped carbon (mNC) was prepared through a facile one-pot carbonization method using the low-cost melamine and polyacrylonitrile as the precursor materials. The obtained mNC material exhibits a high surface area, rich nitrogen content and can be used as an ideal catalyst support to fabricate noble metal modified nanocatalysts. Here, small Ag nanoparticles were supported on the mNC material with high dispersion to give the Ag/mNC nanocatalyst. The obtained Ag/mNC nanocatalyst was used in the catalytic reduction of nitroarenes and showed excellent catalytic activity, probably due to the small Ag NPs which highly dispersed on the fluffy mNC material that can enhance the accessibility and mass transfer, and subsequently enhance the catalytic activity...
July 20, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28727446/reductive-outer-sphere-single-electron-transfer-is-an-exception-rather-than-the-rule-in-natural-and-engineered-chlorinated-ethene-dehalogenation
#10
Benjamin Heckel, Stefan Cretnik, Sarah Kliegman, Orfan Shouakar-Stash, Kristopher McNeill, Martin Elsner
Chlorinated ethenes (CEs) such as perchloroethylene, trichloroethylene and dichloroethylene are notorious groundwater contaminants. Although reductive dehalogenation is key to their environmental and engineered degradation, underlying reaction mechanisms remain elusive. Outer-sphere reductive single electron transfer (OS-SET) has been proposed for such different processes as Vitamin B12-dependent biodegradation and zerovalent metal-mediated dehalogenation. Compound-specific isotope effect ((13)C/(12)C, (37)Cl/(35)Cl) analysis offers a new opportunity to test these hypotheses...
August 16, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28716488/simultaneous-anaerobic-transformation-of-carbon-tetrachloride-to-carbon-dioxide-and-tetrachloroethene-to-ethene-in-a-continuous-flow-column
#11
Mohammad F Azizian, Lewis Semprini
The simultaneous anaerobic transformation of tetrachloroethene (PCE) and carbon tetrachloride (CT) was evaluated in a continuous flow column. The column was packed with quartz sand and bioaugmented with the Evanite culture (EV) that is capable of transforming PCE to ethene. Azizian and Semprini (2016) reported that PCE and CT could be simultaneously transformed in the column, with PCE (0.1mM) transformed mainly to ethene and CT (0.015mM) to chloroform (CF) (20%) and an unknown transformation product, likely carbon dioxide (CO2)...
July 6, 2017: Journal of Contaminant Hydrology
https://www.readbyqxmd.com/read/28715737/static-and-continuous-flow-through-pulsed-light-technology-for-pesticide-abatement-in-water
#12
Ana Beatriz Baranda, Amaia Lasagabaster, Iñigo Martínez de Marañón
Perspectives concerning pulsed light (PL) technology as a novel water decontamination treatment are overviewed in this work. Degradation of atrazine, malathion, chlorpyriphos-methyl and bromopropylate in aqueous solutions at different concentrations was performed employing static and continuous flow-through PL units. Results for both PL systems were compared in terms of efficacy of pesticides degradation and derived photoproducts formed. The pesticides degradation increased with the applied total fluence for both PL systems...
July 8, 2017: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/28690604/phenol-is-the-initial-product-formed-during-growth-and-degradation-of-bromobenzene-by-tropical-marine-yeast-yarrowia-lipolytica-ncim-3589-via-an-early-dehalogenation-step
#13
Aakanksha A Vatsal, Smita S Zinjarde, Ameeta RaviKumar
Bromobenzene (BrB), a hydrophobic, recalcitrant organic compound, is listed by the environmental protection agencies as an environmental and marine pollutant having hepatotoxic, mutagenic, teratogenic, and carcinogenic effects. The tropical marine yeast Yarrowia lipolytica 3589 was seen to grow aerobically on BrB and displayed a maximum growth rate (μmax) of 0.04 h(-1). Furthermore, we also observed an increase in cell size and sedimentation velocity for the cells grown on BrB as compared to the glucose grown cells...
2017: Frontiers in Microbiology
https://www.readbyqxmd.com/read/28689132/new-insights-into-the-spatial-variability-of-biofilm-communities-and-potentially-negative-bacterial-groups-in-hydraulic-concrete-structures
#14
Wei Cai, Yi Li, Lihua Niu, Wenlong Zhang, Chao Wang, Peifang Wang, Fangang Meng
The composition and distribution characteristics of bacterial communities in biofilms attached to hydraulic concrete structure (HCS) surfaces were investigated for the first time in four reservoirs in the middle and lower reaches of the Yangtze River Basin using 16S rRNA Miseq sequencing. High microbial diversity was found in HCS biofilms, and notable differences were observed in different types of HCS. Proteobacteria, Cyanobacteria and Chloroflexi were the predominant phyla, with respective relative abundances of 35...
June 22, 2017: Water Research
https://www.readbyqxmd.com/read/28688846/evaluation-of-nitrate-effects-in-the-aqueous-photodegradability-of-selected-phenolic-pollutants
#15
G Castro, I Rodríguez, M Ramil, R Cela
The effect of nitrate in the aqueous photodegradation of five phenolic environmental pollutants (ortho-phenylphenol, OPP; methyl paraben, MeP; propyl paraben, PrP; Triclosan, TCS and bisphenol A, BPA) is evaluated. Time-course of precursor compounds and formation of transformation products (TPs) were investigated by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). Nitrate showed a positive effect in the removal of selected pollutants. Observed TPs resulted from hydroxylation, aromatic nitration (with or without molecule cleavage) and nitro dehalogenation processes...
October 2017: Chemosphere
https://www.readbyqxmd.com/read/28686268/smi2-mediated-reductive-cyclization-of-%C3%AE-arylthio-ketones-a-facile-and-diastereoselective-synthesis-of-thiochroman-derivatives
#16
Hui Mao, Bing-Xin You, Lie-Jin Zhou, Ting-Ting Xie, Yi-Hang Wen, Xin Lv, Xiao-Xia Wang
SmI2-mediated reductive cyclization of β-arylthio ketones to generate thiochroman derivatives is not a generally observed process and the reported examples are limited to geminal disubstitution in the substrates. The results of the current study show that the cyclization also occurs when other substitution patterns are present, affording a general approach to dihydrothiochroman-ols in good yields and high degrees of diastereoselectivity. Besides, the halogen substitution on β-aryl is tolerated in most cases here although reductive dehalogenation has been reported to predominate in the reductive cyclization process...
July 7, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28671181/cobamide-mediated-enzymatic-reductive-dehalogenation-via-long-range-electron-transfer
#17
Cindy Kunze, Martin Bommer, Wilfred R Hagen, Marie Uksa, Holger Dobbek, Torsten Schubert, Gabriele Diekert
The capacity of metal-containing porphyrinoids to mediate reductive dehalogenation is implemented in cobamide-containing reductive dehalogenases (RDases), which serve as terminal reductases in organohalide-respiring microbes. RDases allow for the exploitation of halogenated compounds as electron acceptors. Their reaction mechanism is under debate. Here we report on substrate-enzyme interactions in a tetrachloroethene RDase (PceA) that also converts aryl halides. The shape of PceA's highly apolar active site directs binding of bromophenols at some distance from the cobalt and with the hydroxyl substituent towards the metal...
July 3, 2017: Nature Communications
https://www.readbyqxmd.com/read/28654328/biochemistry-of-catabolic-reductive-dehalogenation
#18
REVIEW
Maeva Fincker, Alfred M Spormann
A wide range of phylogenetically diverse microorganisms couple the reductive dehalogenation of organohalides to energy conservation. Key enzymes of such anaerobic catabolic pathways are corrinoid and Fe-S cluster-containing, membrane-associated reductive dehalogenases. These enzymes catalyze the reductive elimination of a halide and constitute the terminal reductases of a short electron transfer chain. Enzymatic and physiological studies revealed the existence of quinone-dependent and quinone-independent reductive dehalogenases that are distinguishable at the amino acid sequence level, implying different modes of energy conservation in the respective microorganisms...
June 20, 2017: Annual Review of Biochemistry
https://www.readbyqxmd.com/read/28649683/surface-assisted-ullmann-coupling
#19
M Lackinger
Surface-assisted Ullmann coupling is the workhorse of on-surfaces synthesis. Among the various couplings that were successfully transferred from solution to solid surfaces, Ullmann coupling is arguably the most reliable, controllable, and widespread coupling reaction. The basic reaction scheme is straightforward: halogenated precursors are deposited onto solid surfaces, normally of coinage metals. In the adsorbed state the halogen substitutents are split off by virtue of the surface's reactivity, thereby generating acitvated species that subsequently recombine by forming C-C bonds...
June 26, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28648395/the-complete-genome-of-the-tetrachloroethene-respiring-epsilonproteobacterium-sulfurospirillum-halorespirans
#20
Tobias Goris, Benjamin Schenz, Johannes Zimmermann, Mikael Lemos, Jörg Hackermüller, Torsten Schubert, Gabriele Diekert
Sulfurospirillum halorespirans is a bacterium that couples the reductive dehalogenation of chlorinated ethenes to growth. This process is called organohalide respiration (OHR), which can be of importance for bioremediation. Here, we report the complete genome of S. halorespirans, the second one of an organohalide-respiring Epsilonproteobacterium after that of Sulfurospirillum multivorans. With both genomes at hand, we were able to ascertain that the genomic region encoding OHR proteins in Epsilonproteobacteria differs from that found in organohalide-respiring bacteria (OHRB) affiliated to other phyla and that the production of a unique cobamide, norpseudo-B12, might not be limited to the model organism S...
June 22, 2017: Journal of Biotechnology
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