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1.
Sci Total Environ ; 656: 1063-1070, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30625638

RESUMO

Microcystis aeruginosa (M. aeruginosa) commonly blooms in summer while Cyclotella meneghiniana (C. meneghiniana) outbreaks in fall in water reservoirs of Southeast China. Pre-oxidation has been demonstrated to enhance the algae removal from chemical coagulation processes. However, excessive dosage of pre-oxidant can increase the disinfection by-products formation potential (DBPsFP). Additionally, the DBPs formation mechanisms from algae during the pre-oxidation-coagulation-chlorination processes have not well elucidated. In this study, the objectives were to investigate the trichloromethane (TCM) formation, the changes of water quality indexes, and the morphology changes of algal cells from M. aeruginosa or C. meneghiniana contaminated water during potassium permanganate (KMnO4) or chlorine (Cl2) pre-oxidation-coagulation-chlorination disinfection. The results showed that the TCM yield for two algal species decreased with the dosage increase of KMnO4 pre-oxidation, but increased with the dosage increase of pre-chlorination. Therefore, the 2.0 mg/L KMnO4 or 0.5 mg/L Cl2 was proposed as the optimal dosage for preventing both M. aeruginosa blooms in summer and for C. meneghiniana outbreaks in fall. M. aeruginosa exhibited a slightly higher TCM yield than C. meneghiniana in these treatment processes. Based on the release of potassium (K) ion and SEM analysis, KMnO4 had less damage on cell integrity than Cl2 at the dosage ≤2.0 mg/L. In addition, C. meneghiniana was easier to be disrupted by both pre-oxidants than M. aeruginosa, combining with subsequent coagulation led to different value of dissolved organic carbon (DOC), UV-visible absorbance (UV254) and turbidity.


Assuntos
Cloro/química , Clorofórmio/metabolismo , Diatomáceas/metabolismo , Microcystis/metabolismo , Permanganato de Potássio/química , Purificação da Água/métodos , Diatomáceas/citologia , Diatomáceas/efeitos dos fármacos , Relação Dose-Resposta a Droga , Floculação , Halogenação , Microcystis/citologia , Microcystis/efeitos dos fármacos , Oxidantes/química , Oxirredução , Qualidade da Água
2.
Spectrochim Acta A Mol Biomol Spectrosc ; 209: 186-195, 2019 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-30388588

RESUMO

Camphor is known to be held in the substrate pocket of cytochrome P450cam enzyme via H-bond with a tyrosine residue of the enzyme in a unique orientation. This structural exclusivity results in regio- and stereo-specific hydroxylation of camphor by the enzyme. We have carried out a combined IR spectroscopic and quantum chemical investigation to shed light on the factors influencing the conformational exclusivity of 1R-(+)-camphor in the substrate pocket of Cytochrome P450cam, and to determine whether the selectivity is an inherent property of the substrate itself, or is imposed by the enzyme. For this purpose, complexes of camphor have been studied with three H-bond donors namely phenol, methanol and chloroform. Each of the three donors was found to form stable complexes with two distinct conformers; the one mimicking the conformation in enzyme substrate pocket was found to be more stable of the two, for all three donors. Experimentally, both conformers of the H-bonded complexes were identified separately for phenol and methanol in an argon matrix at 8 K, but not for chloroform due to very small energy barrier for interconversion of the two conformers. In room temperature solution phase spectra of camphor with all three donors, the differences in spectral attributes between the two isomeric H-bonded complexes were lost due to thermal motions.


Assuntos
Cânfora 5-Mono-Oxigenase/química , Cânfora/química , Clorofórmio/química , Metanol/química , Fenol/química , Teoria Quântica , Espectrofotometria Infravermelho/métodos , Sítios de Ligação , Cânfora/metabolismo , Cânfora 5-Mono-Oxigenase/metabolismo , Clorofórmio/metabolismo , Cristalografia por Raios X , Humanos , Ligações de Hidrogênio , Cinética , Metanol/metabolismo , Modelos Moleculares , Fenol/metabolismo , Ligação Proteica , Conformação Proteica , Especificidade por Substrato
3.
Mol Pharm ; 15(9): 3920-3930, 2018 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-30067911

RESUMO

It has been proposed that general anesthesia results from direct multisite interactions with multiple and diverse ion channels in the brain. An understanding of the mechanisms by which general anesthetics modulate ion channels is essential to clarify their underlying behavior and their role in reversible immobilization and amnesia. Despite the fact that volatile general anesthetics are drugs that primarily induce insensitivity to pain, they have been reported to sensitize and active the vanilloid-1 receptor, TRPV1, which is known to mediate the response of the nervous system to certain harmful stimuli and which plays a crucial role in the pain pathway. Currently, the mechanism of action of anesthetics is unknown and the precise molecular sites of interaction have not been identified. Here, using ∼2.5 µs of classical molecular dynamics simulations and metadynamics, we explore these enigmas. Binding sites are identified and the strength of the association is further characterized using alchemical free-energy calculations. Anesthetic binding/unbinding proceeds primarily through a membrane-embedded pathway, and subsequently, a complex scenario is established involving multiple binding sites featuring single or multiple occupancy states of two small volatile drugs. One of the five anesthetic binding sites reported was previously identified experimentally, and another one, importantly, is identical to that of capsaicin, one of the chemical stimuli that activate TRPV1. However, in contrast to capsaicin, isoflurane and chloroform binding free-energies render modest to no association compared to capsaicin, suggesting a different activation mechanism. Uncovering chloroform and isoflurane modulatory sites will further our understanding of the TRPV1 molecular machinery and open the possibility of developing site-specific drugs.


Assuntos
Anestésicos Gerais/metabolismo , Canais de Cátion TRPV/química , Canais de Cátion TRPV/metabolismo , Animais , Sítios de Ligação , Capsaicina/metabolismo , Clorofórmio/metabolismo , Humanos , Isoflurano/metabolismo , Simulação de Dinâmica Molecular , Ligação Proteica , Domínios Proteicos
4.
Methods Enzymol ; 603: 115-128, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29673521

RESUMO

Changes in electron spin content can be detected by X-band continuous-wave electron spin resonance (ESR, EPR) in Drosophila fruit flies without requiring the use of spin traps. The spin changes are related to cellular respiration and behave differently in anesthesia-resistant fly strains. We describe the method used in these measurements and its possible applications to the problem of the mechanism of general anesthesia.


Assuntos
Anestesia Geral/métodos , Anestésicos Gerais/química , Clorofórmio/química , Drosophila melanogaster/genética , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Anestésicos Gerais/metabolismo , Animais , Clorofórmio/metabolismo , Drosophila melanogaster/metabolismo , Proteínas de Insetos/química , Proteínas de Insetos/metabolismo , Melaninas/química , Melaninas/metabolismo , Movimento , Mutação , Neurônios/citologia , Neurônios/metabolismo , Oxigênio/química , Oxigênio/metabolismo , Marcadores de Spin
5.
Chemosphere ; 198: 556-564, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29422245

RESUMO

S,S-ethylenediamine-N,N-disuccinic acid (EDDS) enhanced reductive dissolution of α-FeOOH by Shewanella putrefaciens CN32 (CN32), resulting in formation of surface-bound Fe(II) species (FeIIEDDS) to improve reductive dechlorination of carbon tetrachloride (CT). The pseudo-first-order rate constants for bio-reduction extents of α-FeOOH by CN32 in the presence of 1.36 mM EDDS was 0.023 ±â€¯0.0003 d-1 which was higher than without EDDS. The enhancement mechanism of bio-reduction was attributed to the strong complexation ability of EDDS to formed FeIIIEDDS, which could be better utilized by CN32. The dechlorination kinetic of CT by FeIIEDDS (2.016 h-1) in the presence of 1.36 mM EDDS was 24 times faster than without EDDS. Chloroform were detected as main products for the degradation of CT. The chemical analyses and morphological observation showed that combination between EDDS and Fe2+ produced FeIIEDDS complex, which had a reductive potential of -0.375 V and significantly enhanced CT dechlorination. The results showed that EDDS played an important role in enhancing the bio-reduction of α-FeOOH to accelerate reductive dechlorination of CT.


Assuntos
Tetracloreto de Carbono/metabolismo , Etilenodiaminas/metabolismo , Compostos de Ferro/metabolismo , Minerais/metabolismo , Shewanella putrefaciens/metabolismo , Succinatos/metabolismo , Quelantes/metabolismo , Clorofórmio/metabolismo , Halogenação/fisiologia , Ferro/química , Cinética , Oxirredução
6.
Phytochem Anal ; 29(2): 137-143, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28881407

RESUMO

INTRODUCTION: 3-O-Acetyl-11-keto-ß-boswellic acid (AKBA), one of the pentacyclic triterpenoids, is the main biologically active constituent in the resin of Boswellia sacra and has received significant pharmacological interest in recent years. OBJECTIVE: It was aimed to develop a robust method to quantify the AKBA content in methanolic extracts of different parts of B. sacra plants and in various fractions of its resin exudates through near-infrared spectroscopy (NIRS) coupled with partial least squares regression (PLSR). MATERIAL AND METHODS: The near-infrared (NIR) spectra were used to measure the AKBA standards and B. sacra samples at a wavelength range between 700 and 2500 nm in absorption mode. A PLSR model was built from the obtained spectral data using 70% of the AKBA working standard solutions (training set), ranging from 0.1 ppm to 100 ppm. The final PLSR showed a R2 value of 99% with a root mean square error of cross-validation (RMSECV) value of 0.39% and a R2 value of 99%. RESULTS: The results showed that a 50% CHCl3 /n-hexane sub-fraction has the highest concentration of AKBA (14.8%), followed by 55% CHCl3 /n-hexane (13.6%), and 40% CHCl3 /n-hexane (6.1%). CONCLUSION: As the results achieved with the proposed NIRS methodology are in close agreement to the results of AKBA analysis using HPLC, we suggest that our proposed NIRS method is a fast alternative and non-destructive method for the analysis of AKBA in different samples of B. sacra. Copyright © 2017 John Wiley & Sons, Ltd.


Assuntos
Boswellia/química , Espectroscopia de Luz Próxima ao Infravermelho/métodos , Triterpenos/análise , Clorofórmio/metabolismo , Cromatografia Líquida de Alta Pressão , Hexanos/química , Análise dos Mínimos Quadrados , Modelos Químicos , Estruturas Vegetais/química , Solventes/química , Triterpenos/farmacologia
7.
J Contam Hydrol ; 203: 93-103, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28716488

RESUMO

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). The fermentation of propionate, formed from lactate fermentation, was inhibited after the transformation of CT, likely from the exposure to CF. Reported here is the second phase of that study where a second bioaugmentation of the EV culture was made to reintroduce a lactate and propionate fermenting population to the column. Effective lactate and propionate fermentation were restored with a H2 concentration of ~25nM maintained in the column effluent. PCE (0.1mM) was effectively transformed to ethene (~98%) and vinyl chloride (VC) (~2%). Unlabeled CT (0.015 to 0.03mM) was completely transformed with a transient build-up of CF and chloromethane (CM), which were subsequently removed below their detection limits. A series of transient tests were initiated through the addition of carbon-13 labeled CT (13CT), with concentrations gradually increased from 0.03 to 0.10mM. GC-MS analysis of the column effluent showed that 13C labeled CO2 (13CO2) was formed, ranging from 82 to 93% of the 13CT transformed, with the transient increases in 13CO2 associated with the increased concentration of 13CT. A modified COD analysis indicated a lesser amount of 13CT (18%) was transformed to soluble products, while 13CO2 represented 82% the 13CT transformed. In a final transient test, the influent lactate concentration was decreased from 1.1 to 0.67mM. The transformation of both CT and PCE changed dramatically. Only 59% of the 13CT was transformed, primarily to CF. 13CO2 concentrations gradually decreased to background levels, indicating CO2 was no longer a transformation product. PCE transformation resulted in the following percentage of products formed: cDCE (60%), VC (36%), and ethene (4%). Incomplete propionate fermentation was also observed, consistent with the build-up of CF and the decrease in H2 concentrations to approximately 2nM. The results clearly demonstrate that high concentrations of CT were transformed to CO2, and effective PCE dehalogenation to ethene was maintained when excess lactate was fed and propionate was effectively fermented. However, when the lactate concentration was reduced, both PCE and CT transformation and propionate fermentation were negatively impacted.


Assuntos
Dióxido de Carbono/metabolismo , Tetracloreto de Carbono/metabolismo , Etilenos/metabolismo , Tetracloroetileno/metabolismo , Anaerobiose , Biodegradação Ambiental , Reatores Biológicos/microbiologia , Dióxido de Carbono/química , Isótopos de Carbono/análise , Tetracloreto de Carbono/química , Clorofórmio/química , Clorofórmio/metabolismo , Etilenos/química , Halogenação , Tetracloroetileno/química , Cloreto de Vinil/química , Cloreto de Vinil/metabolismo , Poluentes Químicos da Água/química , Poluentes Químicos da Água/metabolismo
8.
Microb Biotechnol ; 10(6): 1640-1648, 2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-28631300

RESUMO

We report herein the purification of a chloroform (CF)-reducing enzyme, TmrA, from the membrane fraction of a strict anaerobe Dehalobacter sp. strain UNSWDHB to apparent homogeneity with an approximate 23-fold increase in relative purity compared to crude lysate. The membrane fraction obtained by ultracentrifugation was solubilized in Triton X-100 in the presence of glycerol, followed by purification by anion exchange chromatography. The molecular mass of the purified TmrA was determined to be 44.5 kDa by SDS-PAGE and MALDI-TOF/TOF. The purified dehalogenase reductively dechlorinated CF to dichloromethane in vitro with reduced methyl viologen as the electron donor at a specific activity of (1.27 ± 0.04) × 103 units mg protein-1 . The optimum temperature and pH for the activity were 45°C and 7.2, respectively. The UV-visible spectrometric analysis indicated the presence of a corrinoid and two [4Fe-4S] clusters, predicted from the amino acid sequence. This is the first report of the production, purification and biochemical characterization of a CF reductive dehalogenase.


Assuntos
Proteínas de Bactérias/química , Proteínas de Bactérias/isolamento & purificação , Clorofórmio/metabolismo , Clostridiales/enzimologia , Oxirredutases/química , Oxirredutases/isolamento & purificação , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Cromatografia por Troca Iônica , Clostridiales/química , Clostridiales/genética , Estabilidade Enzimática , Concentração de Íons de Hidrogênio , Cinética , Peso Molecular , Oxirredutases/genética , Oxirredutases/metabolismo , Especificidade por Substrato
9.
Chem Asian J ; 12(16): 1997-2007, 2017 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-28569439

RESUMO

It is well established that the majority of chlorinated organic substances found in the terrestrial environment are produced naturally. The presence of these compounds in soils is not limited to a single ecosystem. Natural chlorination is also a widespread phenomenon in grasslands and agricultural soils typical for unforested areas. These chlorinated compounds are formed from chlorination of natural organic matter consisting of very complex chemical structures, such as lignin. Chlorination of several lignin model compounds results in the intermediate formation of trichloroacetyl-containing compounds, which are also found in soils. These decay, in general, through a haloform-type reaction mechanism to CHCl3 . Upon release into the atmosphere, CHCl3 will produce chlorine radicals through photolysis, which will, in turn, lead to natural depletion of ozone. There is evidence that fungal chloroperoxidases able to produce HOCl are involved in the chlorination of natural organic matter. The objective of this review is to clarify the role and source of the various chloroperoxidases involved in the natural formation of CHCl3 .


Assuntos
Cloreto Peroxidase/metabolismo , Compostos Clorados/síntese química , Clorofórmio/síntese química , Meio Ambiente , Cloreto Peroxidase/química , Compostos Clorados/química , Compostos Clorados/metabolismo , Clorofórmio/química , Clorofórmio/metabolismo , Fungos/química , Fungos/enzimologia , Fotólise , Solo/química
10.
Chemosphere ; 182: 65-75, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28494362

RESUMO

Carbon tetrachloride (CT) and chloroform (CF) were transformed in batch reactor experiments conducted with anaerobic dechlorinating cultures and supernatant (ADC + S) harvested from continuous flow reactors. The Evanite (EV) and Victoria/Stanford (VS) cultures, capable of respiring trichloroethene (TCE), 1,2-cis-dichloroethene (cDCE), and vinyl chloride (VC) to ethene (ETH), were grown in continuous flow reactors receiving an influent feed of saturated TCE (10 mM; 60 mEq) and formate (45 mM; 90 mEq) but no CT or CF. Cells and supernatant were harvested from the chemostats and inoculated into batch reactors at the onset of each experiment. CT transformation was complete following first order kinetics with CF, DCM and CS2 as the measurable transformation products, representing 20-40% of the original mass of CT, with CO2 likely the unknown transformation product. CF was transformed to DCM and likely CO2 at an order of magnitude rate lower than CT, while DCM was not further transformed. An analytical first order model including multiple key reactions effectively simulated CT transformation, product formation and transformation, and provided reasonable estimates of transformation rate coefficients. Biotic and abiotic treatments indicated that CT was mainly transformed via abiotic processes. However, the presence of live cells was associated with the transformation of CF to DCM. In biotic tests both TCE and CT were simultaneously transformed, with TCE transformed to ETH and approximately 15-53% less CF formed via CT transformation. A 14-day exposure to CF (CFmax = 1.4 µM) reduced all rates of chlorinated ethene respiration by a factor of 10 or greater.


Assuntos
Bactérias Anaeróbias/metabolismo , Tetracloreto de Carbono/metabolismo , Clorofórmio/metabolismo , Halogenação , Tricloroetileno/metabolismo , Biodegradação Ambiental , Reatores Biológicos , Etilenos , Formiatos , Cinética , Taxa Respiratória , Cloreto de Vinil
11.
J Exp Biol ; 220(Pt 8): 1396-1399, 2017 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-28167802

RESUMO

The integument protects the organism against penetration of xenobiotics and water that would potentially interfere with homeostasis. In insects that play key roles in a variety of agricultural and ecological habitats, this inward barrier has barely been investigated. In order to advance knowledge in this field, we studied integumental barrier (cuticle) permeability in the two global pests Trialeurodes vaporariorum (greenhouse whitefly) and Cimex lectularius (bedbug), applying a simple dye-penetration assay. In agreement with our recent findings in Drosophila melanogaster, we show that the surface of these insects is regionalised. We also show that, in contrast to the single barrier in D. melanogaster, two barriers with distinct temperature-sensitive and lipid-based physico-chemical material properties act in parallel to protect these insects against penetration of hydrophilic molecules. These findings imply the existence of unexplored mechanisms by which the cuticle acts as a protective coat against the penetration of water and xenobiotics, including pollutants and insecticides.


Assuntos
Percevejos-de-Cama/metabolismo , Hemípteros/metabolismo , Animais , Percevejos-de-Cama/anatomia & histologia , Percevejos-de-Cama/química , Azul de Bromofenol/metabolismo , Clorofórmio/metabolismo , Amarelo de Eosina-(YS)/metabolismo , Hemípteros/anatomia & histologia , Hemípteros/química , Metabolismo dos Lipídeos , Lipídeos/química , Azul de Metileno/metabolismo , Permeabilidade , Temperatura Ambiente , Água/metabolismo , Asas de Animais/anatomia & histologia , Asas de Animais/química , Asas de Animais/metabolismo , Xenobióticos/metabolismo
12.
Cold Spring Harb Protoc ; 2017(1)2017 01 03.
Artigo em Inglês | MEDLINE | ID: mdl-28049781

RESUMO

The isolation of DNA from bacteria, described in this protocol, relies upon the use of sodium dodecyl sulfate and proteinase K to lyse the cells. High-molecular-weight DNA is then sheared (to reduce its viscosity and make it more manageable), extracted with phenol:chloroform, and precipitated with isopropanol. DNA isolated according to this procedure ranges from 30 to 80 kb in length.


Assuntos
DNA Bacteriano/isolamento & purificação , Bactérias Gram-Negativas/química , Bactérias Gram-Negativas/genética , Biologia Molecular/métodos , 2-Propanol , Bacteriólise , Clorofórmio/metabolismo , DNA Bacteriano/genética , Detergentes/metabolismo , Endopeptidase K/metabolismo , Fenol/metabolismo , Dodecilsulfato de Sódio/metabolismo , Solventes/metabolismo
13.
ISME J ; 11(3): 626-640, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-27898054

RESUMO

Two novel chlorinated alkane-respiring Dehalobacter restrictus strains CF and DCA were isolated from the same enrichment culture, ACT-3, and characterized. The closed genomes of these highly similar sister strains were previously assembled from metagenomic sequence data and annotated. The isolation of the strains enabled experimental verification of predicted annotations, particularly focusing on irregularities or predicted gaps in central metabolic pathways and cofactor biosynthesis. Similar to D. restrictus strain PER-K23, strains CF and DCA require arginine, histidine and threonine for growth, although the corresponding biosynthesis pathways are predicted to be functional. Using strain CF to experimentally verify annotations, we determined that the predicted defective serine biosynthesis pathway can be rescued with a promiscuous serine hydroxymethyltransferase. Strain CF grew without added thiamine although the thiamine biosynthesis pathway is predicted to be absent; intracellular thiamine diphosphate, the cofactor of carboxylases in central metabolism, was not detected in cell extracts. Thus, strain CF may use amino acids to replenish central metabolites, portending entangled metabolite exchanges in ACT-3. Consistent with annotation, strain CF possesses a functional corrinoid biosynthesis pathway, demonstrated by increasing corrinoid content during growth and guided cobalamin biosynthesis in corrinoid-free medium. Chloroform toxicity to corrinoid-producing methanogens and acetogens may drive the conservation of corrinoid autotrophy in Dehalobacter strains. Heme detection in strain CF cell extracts suggests the 'archaeal' heme biosynthesis pathway also functions in anaerobic Firmicutes. This study reinforces the importance of incorporating enzyme promiscuity and cofactor availability in genome-scale functional predictions and identifies essential nutrient interdependencies in anaerobic dechlorinating microbial communities.


Assuntos
Peptococcaceae/isolamento & purificação , Peptococcaceae/metabolismo , Microbiologia da Água , Processos Autotróficos , Vias Biossintéticas , Biotina/biossíntese , Clorofórmio/metabolismo , Corrinoides/biossíntese , Heme/biossíntese , Peptococcaceae/classificação
14.
Biodegradation ; 27(4-6): 223-236, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27351716

RESUMO

Site in a former chemical manufacture plant in China was found contaminated with high level of chlorinated volatile organic compounds (CVOCs). The major contaminants chloroform (CF), 1,2-dichloroethane (1,2-DCA) and vinyl chloride (VC) in groundwater were up to 4.49 × 104, 2.76 × 106 and 4.35 × 104 µg/L, respectively. Ethene and methane were at concentrations up to 2219.80 and 165.85 µg/L, respectively. To test the hypothesis that the CVOCs in groundwater at this site could be removed via biodegradation, biomarker analyses and microcosm studies were conducted. Dehalococcoides 16S rRNA gene and VC-reductase gene vcrA at densities up to 1.5 × 104 and 3.2 × 104 copies/L were detected in some of the groundwater samples, providing strong evidence that dechlorinating bacteria were present in the aquifer. Results from the microcosm studies showed that at moderate concentrations (CF about 4000 µg/L and 1,2-DCA about 100 µg/L), CF was recalcitrant under natural condition but was degraded under biostimulation and bioaugmentation, while 1,2-DCA was degraded under all the three conditions. At high concentration (CF about 1,000,000 µg/L and 1,2-DCA about 20,000 µg/L), CF was recalcitrant under all the three treatments and 1,2-DCA was only degraded under bioaugmentation, indicating that high concentrations of contaminants were inhibitory to the bacteria. Electron donors had influence on the degradation of contaminants. Of the four fatty acids (pyruvate, acetate, propionate and lactate) examined, all could stimulate the degradation of 1,2-DCA at both moderate and high concentrations, whereas only pyruvate and acetate could stimulate the degradation of CF at moderate concentration. In the microcosms, the observed first-order degradation rates of CF and 1,2-DCA were up to 0.12 and 0.11/day, respectively. Results from the present study provided scientific basis for remediating CVOCs contaminated groundwater at the site.


Assuntos
Bactérias/metabolismo , Água Subterrânea/análise , Compostos Orgânicos Voláteis/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Biodegradação Ambiental , Clorofórmio/isolamento & purificação , Clorofórmio/metabolismo , Dicloretos de Etileno/isolamento & purificação , Dicloretos de Etileno/metabolismo , Compostos Orgânicos Voláteis/metabolismo , Poluentes Químicos da Água/metabolismo
15.
J Contam Hydrol ; 190: 58-68, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27183341

RESUMO

Tetrachloroethene (PCE) and carbon tetrachloride (CT) were simultaneously transformed in a packed column that was bioaugmented with the Evanite culture (EV). The data presented here have been obtained over a period of 1930days. Initially the column was continuously fed synthetic groundwater with PCE (0.1mM), sulfate (SO4(2-)) (0.2mM) and formate (2.1mM) or lactate (1.1mM), but not CT. In these early stages of the study the effluent H2 concentrations ranged from 7 to 19nM, and PCE was transformed to ethene (ETH) (81 to 85%) and vinyl chloride (VC) (11 to 17%), and SO4(2-) was completely reduced when using either lactate or formate as electron donors. SO4(2-) reduction occurred concurrently with cis-DCE and VC dehalogenation. Formate was a more effective substrate for promoting dehalogenation based on electron donor utilization efficiency. Simultaneous PCE and CT tests found CT (0.015mM) was completely transformed with 20% observed as chloroform (CF) and trace amounts of chloromethane (CM) and dichloromethane (DCM), but no methane (CH4) or carbon disulfide (CS2). PCE transformation to ETH improved with CT addition in response to increases in H2 concentrations to 160nM that resulted from acetate formation being inhibited by either CT or CF. Lactate fermentation was negatively impacted after CT transformation tests, with propionate accumulating, and H2 concentrations being reduced to below 1nM. Under these conditions both SO4(2-) reduction and dehalogenation were negatively impacted, with sulfate reduction not occurring and PCE being transformed to cis-dichloroethene (c-DCE) (52%) and VC (41%). Upon switching to formate, H2 concentrations increased to 40nM, and complete SO4(2-) reduction was achieved, while PCE was transformed to ETH (98%) and VC (1%), with no acetate detected. Throughout the study PCE dehalogenation to ethene was positively correlated with the effluent H2 concentrations.


Assuntos
Tetracloreto de Carbono/metabolismo , Água Subterrânea/química , Tetracloroetileno/metabolismo , Poluentes Químicos da Água/metabolismo , Purificação da Água/métodos , Acetatos/metabolismo , Anaerobiose , Biodegradação Ambiental , Clorofórmio/metabolismo , Etilenos/metabolismo , Formiatos/química , Halogenação , Metano/metabolismo , Consórcios Microbianos , Oxirredução , Cloreto de Vinil/metabolismo
16.
Environ Microbiol ; 18(9): 3092-105, 2016 09.
Artigo em Inglês | MEDLINE | ID: mdl-26970344

RESUMO

Dehalobacter sp. strain UNSWDHB can dechlorinate up to 4 mM trichloromethane at a rate of 0.1 mM per day to dichloromethane and 1,1,2-trichloroethane (1 mM, 0.1 mM per day) with the unprecedented product profile of 1,2-dichloroethane and vinyl chloride. 1,1,1-trichloroethane and 1,1-dichloroethane were slowly utilized by strain UNSWDHB and were not completely removed, with minimum threshold concentrations of 0.12 mM and 0.07 mM respectively under growth conditions. Enzyme kinetic experiments confirmed strong substrate affinity for trichloromethane and 1,1,2-trichloroethane (Km = 30 and 62 µM respectively) and poor substrate affinity for 1,1,1-trichloroethane and 1,1-dichloroethane (Km = 238 and 837 µM respectively). Comparison of enzyme kinetic and growth data with other trichloromethane respiring organisms (Dehalobacter sp. strain CF and Desulfitobacterium sp. strain PR) suggests an adaptation of strain UNSWDHB to trichloromethane. The trichloromethane RDase (TmrA) expressed by strain UNSWDHB was identified by BN-PAGE and functionally characterized. Amino acid comparison of homologous RDases from all three organisms revealed only six significant amino acid substitutions/deletions, which are likely to be crucial for substrate specificity. Furthermore, strain UNSWDHB was shown to grow without exogenous supply of cobalamin confirming genomic-based predictions of a fully functional cobalamin synthetic pathway.


Assuntos
Clorofórmio/metabolismo , Etano/metabolismo , Peptococcaceae/metabolismo , Dicloretos de Etileno/metabolismo , Halogenação , Cloreto de Metileno/metabolismo , Peptococcaceae/genética , Peptococcaceae/isolamento & purificação , Tricloroetanos/metabolismo
17.
Lett Appl Microbiol ; 61(4): 346-53, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26119060

RESUMO

UNLABELLED: The mechanisms and organisms involved in the natural formation of volatile organohalogen compounds (VOX) are largely unknown. We provide evidence that the common and widespread soil bacterium Sinorhizobium meliloti strain 1021 is capable of producing up to 3338·6 ± 327·8 ng l(-1) headspace volume of chloroform (CHCl3 ) and 807·8 ± 13·5 ng l(-1)  headspace volume of tetrachloroethene (C2 Cl4 ) within 1 h when grown in soil extract medium. Biotic VOX formation has been suggested to be linked to the activity of halogenating enzymes such as haloperoxidases. We tested if the observed VOX formation by S. meliloti can be attributed to one of its chloroperoxidases (Smc01944) that is highly expressed in the presence of H2 O2. However, addition of 10 mmol l(-1) H2 O2 to the S. meliloti cultures decreased VOX formation by 52% for chloroform and 25% for tetrachloroethene, while viable cell numbers decreased by 23%. Interestingly, smc01944 gene expression increased 450-fold. The quantification of extracellular chlorination activity in cell suspension experiments did not provide evidence for a role of S. meliloti chloroperoxidases in the observed VOX formation. This suggests that a momentarily unknown mechanism which requires no H2 O2 might be responsible for the VOX formation by S. meliloti. Regardless of the underlying mechanism our results suggest that the soil bacterium S. meliloti might be an important source of VOX in soils. SIGNIFICANCE AND IMPACT OF THE STUDY: Volatile organohalogen compounds (VOX) strongly influence atmospheric chemistry and Earth's climate. Besides anthropogenic emissions they are naturally produced by either abiotic or biotic pathways in various environments. Particularly in soils, microbial processes drive the natural halogen cycle but the direct link to microbial VOX formation has not been studied in detail yet. In this study we provide evidence that the common and widespread soil bacterium Sinorhizobium meliloti strain 1021 forms chloroform and tetrachloroethene. The potential contribution of S. meliloti to soil VOX release could significantly influence soil and atmospheric chemistry.


Assuntos
Cloreto Peroxidase/metabolismo , Clorofórmio/metabolismo , Peróxido de Hidrogênio/metabolismo , Sinorhizobium meliloti/metabolismo , Microbiologia do Solo , Tetracloroetileno/metabolismo , Compostos Orgânicos Voláteis/metabolismo , Sinorhizobium meliloti/genética , Solo
18.
Environ Sci Technol ; 49(7): 4481-9, 2015 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-25764054

RESUMO

The role of bacteria and zerovalent iron (Fe(0)) in the degradation of chlorinated solvents in subsurface environments is of interest to researchers and remediation practitioners alike. Fe(0) used in reactive iron barriers for groundwater remediation positively interacted with enrichment cultures containing Dehalobacter strains in the transformation of halogenated methanes. Chloroform transformation and dichloromethane formation was up to 8-fold faster and 14 times higher, respectively, when a Dehalobacter-containing enrichment culture was combined with Fe(0) compared with Fe(0) alone. The dichloromethane-fermenting culture transformed dichloromethane up to three times faster with Fe(0) compared to without. Compound-specific isotope analysis was employed to compare abiotic and biotic chloroform and dichloromethane degradation. The isotope enrichment factor for the abiotic chloroform/Fe(0) reaction was large at -29.4 ± 2.1‰, while that for chloroform respiration by Dehalobacter was minimal at -4.3 ± 0.45‰. The combined abiotic/biotic dechlorination was -8.3 ± 0.7‰, confirming the predominance of biotic dechlorination. The enrichment factor for dichloromethane fermentation was -15.5 ± 1.5‰; however, in the presence of Fe(0) the factor increased to -23.5 ± 2.1‰, suggesting multiple mechanisms were contributing to dichloromethane degradation. Together the results show that chlorinated methane-metabolizing organisms introduced into reactive iron barriers can have a significant impact on trichloromethane and dichloromethane degradation and that compound-specific isotope analysis can be employed to distinguish between the biotic and abiotic reactions involved.


Assuntos
Clorofórmio/metabolismo , Ferro/metabolismo , Cloreto de Metileno/metabolismo , Peptococcaceae/metabolismo , Poluentes Químicos da Água/metabolismo , Biodegradação Ambiental , Clorofórmio/química , Água Subterrânea/microbiologia , Halogenação , Metano/química , Metano/metabolismo , Cloreto de Metileno/química , Poluentes Químicos da Água/química
19.
Water Res ; 67: 66-76, 2014 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-25262551

RESUMO

Uncertainty regarding changes in dissolved organic carbon (DOC) quantity and quality has created interest in managing peatlands for their ecosystem services such as drinking water provision. The evidence base for such interventions is, however, sometimes contradictory. We performed a laboratory climate manipulation using a factorial design on two dominant peatland vegetation types (Calluna vulgaris and Sphagnum Spp.) and a peat soil collected from a drinking water catchment in Exmoor National Park, UK. Temperature and rainfall were set to represent baseline and future conditions under the UKCP09 2080s high emissions scenario for July and August. DOC leachate then underwent standard water treatment of coagulation/flocculation before chlorination. C. vulgaris leached more DOC than Sphagnum Spp. (7.17 versus 3.00 mg g(-1)) with higher specific ultraviolet (SUVA) values and a greater sensitivity to climate, leaching more DOC under simulated future conditions. The peat soil leached less DOC (0.37 mg g(-1)) than the vegetation and was less sensitive to climate. Differences in coagulation removal efficiency between the DOC sources appears to be driven by relative solubilisation of protein-like DOC, observed through the fluorescence peak C/T. Post-coagulation only differences between vegetation types were detected for the regulated disinfection by-products (DBPs), suggesting climate change influence at this scale can be removed via coagulation. Our results suggest current biodiversity restoration programmes to encourage Sphagnum Spp. will result in lower DOC concentrations and SUVA values, particularly with warmer and drier summers.


Assuntos
Calluna/química , Carbono/metabolismo , Mudança Climática , Água Potável/química , Solo/química , Sphagnopsida/química , Purificação da Água/métodos , Acetonitrilos/metabolismo , Clorofórmio/metabolismo , Simulação por Computador , Conservação dos Recursos Naturais/métodos , Fluorescência , Estações do Ano
20.
Cell Biochem Biophys ; 70(1): 93-101, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24913236

RESUMO

The binding of ciprofloxacin (CFX) to human serum albumin (HSA) has been investigated by fluorescence displacement and induced circular dichroism (ICD) measurements. Displacement measurements were performed with CFX in the absence and presence of marker ligands (hemin for domain I, bilirubin for interspace of domain IA and IIA, chloroform for domain II, and diazepam for domain III) to establish CFX binding site in one of the three major domains of HSA. The primary binding site of CFX is located in site I of HSA (domain IIA) in close vicinity to the site where chloroform (CHCl3) binds. It is depicted from the decrease in quenching constant of HSA-CHCl3 system (0.02 ± 0.06) × 10(-3 )L mol(-1) compared to HSA-CFX-CHCl3 system (0.01 ± 0.06) × 10(-3 )L mol(-1) as obtained by the fluorescence displacement spectroscopy. Furthermore, far-UV CD results show that the binding of CFX leads to change in the helicity of HSA. The ICD results indicated that the CFX binds to the domain IIA of HSA which is in agreement with the fluorescence displacement results.


Assuntos
Antibacterianos/metabolismo , Ciprofloxacino/metabolismo , Albumina Sérica/metabolismo , Análise Espectral , Antibacterianos/farmacologia , Bilirrubina/metabolismo , Sítios de Ligação , Clorofórmio/metabolismo , Ciprofloxacino/farmacologia , Diazepam/metabolismo , Hemina/metabolismo , Humanos , Concentração de Íons de Hidrogênio , Ligação Proteica/efeitos dos fármacos , Estrutura Secundária de Proteína/efeitos dos fármacos , Albumina Sérica/química
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