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Ralf Rabus - One of the best experts on this subject based on the ideXlab platform.
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solvent stress response of the denitrifying bacterium aromatoleum aromaticum strain ebn1
Applied and Environmental Microbiology, 2008Co-Authors: Ralf Rabus, Simon Kuhner, Lars Wohlbrand, Kathleen Trautwein, Thomas Halder, Kenny Kuchta, Alexander SteinbuchelAbstract:The denitrifying betaproteobacterium “Aromatoleum aromaticum” strain EbN1 degrades several aromatic compounds, including Ethylbenzene, toluene, p-cresol, and phenol, under anoxic conditions. The hydrophobicity of these aromatic solvents determines their toxic properties. Here, we investigated the response of strain EbN1 to aromatic substrates at semi-inhibitory (about 50% growth inhibition) concentrations under two different conditions: first, during anaerobic growth with Ethylbenzene (0.32 mM) or toluene (0.74 mM); and second, when anaerobic succinate-utilizing cultures were shocked with Ethylbenzene (0.5 mM), toluene (1.2 mM), p-cresol (3.0 mM), and phenol (6.5 mM) as single stressors or as a mixture (total solvent concentration, 2.7 mM). Under all tested conditions impaired growth was paralleled by decelerated nitrate-nitrite consumption. Additionally, alkylbenzene-utilizing cultures accumulated poly(3-hydroxybutyrate) (PHB) up to 10% of the cell dry weight. These physiological responses were also reflected on the proteomic level (as determined by two-dimensional difference gel electrophoresis), e.g., up-regulation of PHB granule-associated phasins, cytochrome cd1 nitrite reductase of denitrification, and several proteins involved in oxidative (e.g., SodB) and general (e.g., ClpB) stress responses.
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Functional genomics of an anaerobic aromatic-degrading denitrifying bacterium, strain EbN1
Applied Microbiology and Biotechnology, 2005Co-Authors: Ralf RabusAbstract:Nitrate-reducing bacteria of the recently recognized Azoarcus / Thauera group within the Betaproteobacteria contribute significantly to the biodegradation of aromatic and other refractory compounds in anoxic waters and soils. Strain EbN1 belongs to a distinct cluster (new genus) and is the first member of this phylogenetic group, the genome of which has been determined (4.7 Mb; one chromosome, two plasmids) by [Rabus R, Kube M, Heider J, Beck A, Heitmann K, Widdel F, Reinhardt R (2005) The genome sequence of an anaerobic aromatic-degrading denitrifying bacterium, strain EbN1. Arch Microbiol 183:27–36]. Ten anaerobic and four aerobic aromatic-degradation pathways were recognized on the chromosome, with the coding genes mostly forming clusters. Presence of paralogous gene clusters (e.g. for anaerobic Ethylbenzene degradation) suggests an even broader degradation spectrum than previously known. Metabolic versatility is also reflected by the presence of multiple respiratory complexes and is apparently controlled by an extensive regulatory network. Strain EbN1 is unique for its capacity to degrade toluene and Ethylbenzene anaerobically via completely different pathways. Bioinformatical analysis of their genetic blueprints and global expression analysis (DNA-microarray and proteomics) of substrate-adapted cells [Kühner S, Wöhlbrand L, Fritz I, Wruck W, Hultschig C, Hufnagel P, Kube M, Reinhardt R, Rabus R (2005) Substrate-dependent regulation of anaerobic degradation pathways for toluene and Ethylbenzene in a denitrifying bacterium, strain EbN1. J Bacteriol 187:1493–1503] indicated coordinated vs sequential modes of regulation for the toluene and Ethylbenzene pathways, respectively.
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substrate dependent regulation of anaerobic degradation pathways for toluene and Ethylbenzene in a denitrifying bacterium strain ebn1
Journal of Bacteriology, 2005Co-Authors: Simon Kuhner, Lars Wohlbrand, Ingo Fritz, Wasco Wruck, Claus Hultschig, Peter Hufnagel, Michael Kube, Richard Reinhardt, Ralf RabusAbstract:Anaerobic biodegradation of toluene and Ethylbenzene is of environmental concern and biochemical interest due to toxicity and novel reactions, respectively. The denitrifying strain EbN1 is unique in anaerobically degrading both alkylbenzenes via different pathways which converge at benzoyl coenzyme A. The organization of genes involved in both pathways was only recently determined for strain EbN1. In the present study, global expression analysis (DNA microarray and proteomics) indicated involvement of several thus-far-unknown proteins in the degradation of both alkylbenzenes. For example, orf68 and orf57, framing the ebd operon, are implicated in Ethylbenzene degradation, and the ebA1932 and ebA1936 genes, located 7.2 kb upstream of the bbs operon, are implicated in toluene degradation. In addition, expression studies were now possible on the level of the complete pathways. Growth experiments demonstrated that degradative capacities for toluene and Ethylbenzene could be simultaneously induced, regardless of the substrate used for adaptation. Regulation was studied at the RNA (real-time reverse transcription-PCR and DNA microarray) and protein (two-dimensional-difference gel electrophoresis) level by using cells adapted to anaerobic growth with benzoate, toluene, Ethylbenzene, or a mixture of toluene and Ethylbenzene. Expression of the two toluene-related operons (bss and bbs) was specifically induced in toluene-adapted cells. In contrast, genes involved in anaerobic Ethylbenzene degradation were induced in Ethylbenzene- and toluene-adapted cells, suggesting that toluene may act as a gratuitous inducer. In agreement with the predicted sequential regulation of the Ethylbenzene pathway, Ebd proteins (encoding subunits of Ethylbenzene dehydrogenase) were formed in Ethylbenzene- but not in acetophenone-adapted cells, while Apc proteins (subunits of predicted acetophenone carboxylase) were formed under both conditions.
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initial reactions of anaerobic metabolism of alkylbenzenes in denitrifying and sulfate reducing bacteria
Archives of Microbiology, 1998Co-Authors: Ralf Rabus, Johann HeiderAbstract:The initial activation reactions of anaerobic oxidation of the aromatic hydrocarbons toluene and Ethylbenzene were investigated in cell extracts of a toluene-degrading, sulfate-reducing bacterium, Desulfobacula toluolica, and in cell extracts of strain EbN1, a denitrifying bacterium capable of degrading toluene and Ethylbenzene. Extracts of toluene-grown cells of both species catalysed the addition of fumarate to the methyl group of [phenyl-14C]-toluene and formed [14C]-labeled benzylsuccinate. Extracts of Ethylbenzene-grown cells of strain EbN1 did not catalyse this reaction, but catalysed the formation of 1-phenylethanol and acetophenone from [methylene-14C]-Ethylbenzene. Toluene-grown cells of D. toluolica and strain EbN1 synthesised highly induced polypeptides corresponding to the large subunits of benzylsuccinate synthase from Thauera aromatica. These polypeptides were absent in strain EbN1 after growth on Ethylbenzene, although a number of different polypeptides were highly induced. Thus, formation of benzylsuccinate from toluene and fumarate appears to be the general initiating step in anaerobic toluene degradation by bacteria affiliated with the phylogenetically distinct β-subclass (strain EbN1 and T. aromatica) and δ-subclass (D. toluolica) of the Proteobacteria. Anaerobic Ethylbenzene oxidation proceeds via a different pathway involving a two-step oxidation of the methylene group to an alcohol and an oxo group; these steps are most probably followed by a biotin-independent carboxylation reaction and thiolytic cleavage.
Zilin Chen - One of the best experts on this subject based on the ideXlab platform.
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polydopamine assisted immobilization of a zinc ii derived metal organic cage as a stationary phase for open tubular capillary electrochromatography
Mikrochimica Acta, 2019Co-Authors: Zilin Chen, Zhenkun MaoAbstract:A capillary column was modified with a soluble zinc(II)-derived metal-organic cage (MOC) [Zn2L] as the stationary phase to obtain a new coating layer for use in open-tubular capillary electrochromatography. The inner surface of the capillary was first coated with a layer of polydopamine. Then, a solution of the MOC in dichloromethane was introduced into the capillary upon which it is bonded both covalently and non-covalently. The resulting coating layer on the capillary was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The results demonstrated the successful formation of the [Zn2L] modified open-tubular column. The column showed good separation performance towards neutral compounds (such as mEthylbenzene, Ethylbenzene, n-propylbenzene and n-butylbenzene), acidic drugs (such as ibuprofen, ketoprofen, flurbiprofen and diclofenac sodium), food additives (such as parabens, vanillin and related phenolic compounds) and small biomolecules (such as nucleosides and nucleotide bases) by π-interaction and hydrophobic interaction. It also exhibited good precision, the relative standard deviations of the retention time for intra-day, inter-day runs and column-to-column being <1.6%, 2.8%, and 4.0%, respectively. Graphical abstract Schematic presentation of the open-tubular column modified with zinc(II)-derived metal-organic cage by polydopamine-assisted strategy onto the inner wall of capillary for electrochromatographic separations.
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novel zn based mofs stationary phase with large pores for capillary electrochromatography
Electrophoresis, 2016Co-Authors: Tao Bao, Zilin Chen, Pingxiu TangAbstract:Metal-organic frameworks (MOFs) are attractive stationary phases in the field of separation sciences for their unique properties such as large specific surface areas, high porosity, and diverse structures. However, there are few MOFs, which have ultrahigh porosities and gas uptake capacities. In this work, MOF-180 with exceptional porosity, a cage size of 15 × 23 A, was grown on inner wall of capillary as a novel stationary phase for open-tubular CEC. It has been demonstrated that the MOF-180-modified capillary column exhibited good performance for separation of acidic, basic, and neutral analytes. As compared with MOF-199-modified column, MOF-180-modified column exhibited specific recognition and size selectivity to the tested compounds. The characteristics observed by SEM and FTIR indicated that MOF-180 was successfully grafted on the inner wall of the capillary. The precisions (RSDs) of retention time, peak area, and W1/2 for mEthylbenzene, Ethylbenzene, n-propylbenzene, chlorobenzene, o-dichlorobenzene, and 1,2,4-trichlorobenzene were 0.50-0.54%, 3.31-4.13%, 0.35-1.61%, 1.73-4.22%, 2.67-4.37%, and 1.60-3.38%, respectively. Besides, the run-to-run, day-to-day, and column-to-column RSDs of EOF were 0.6%, 4.19%, and 4.31%, respectively.
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growth of metal organic framework hkust 1 in capillary using liquid phase epitaxy for open tubular capillary electrochromatography and capillary liquid chromatography
Journal of Chromatography A, 2015Co-Authors: Tao Bao, Juan Zhang, Wenpeng Zhang, Zilin ChenAbstract:Much attention is being paid to applying metal-organic frameworks (MOFs) as stationary phases in chromatography because of their fascinating properties, such as large surface-to-volume ratios, high levels of porosity, and selective adsorption. HKUST-1 is one of the best-studied face-centered-cubic MOF containing nano-sized channels and side pockets for film growth. However, growth of HKUST-1 framework inside capillary column as stationary phase for capillary electrochromatography is a challenge work. In this work, we carry out the growth of HKUST-1 on the inner wall of capillary by using liquid-phase epitaxy process at room temperature. The fabricated HKUST-1@capillary can be successfully used for the separation of substituted benzene including mEthylbenzene, Ethylbenzene, styrene, chlorobenzene, bromobenzene, o-dichlorobenzene, benzene series, phenolic acids, and benzoic acids derivates. High column efficiency of 1.5×10(5) N/m for mEthylbenzene was achieved. The formation of HKUST-1 grown in the capillary was confirmed and characterized by scanning electron microscopy images, Fourier transform infrared spectra and X-ray diffraction. The column showed long lifetime and excellent stability. The relative standard deviations for intra-day and inter-day repeatability of the HKUST-1@capillary were lower than 7%.
J T C Grotenhuis - One of the best experts on this subject based on the ideXlab platform.
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bioremediation of btex hydrocarbons effect of soil inoculation with the toluene growing fungus cladophialophora sp strain t1
Biodegradation, 2004Co-Authors: Francesc X Prenafetaboldu, Hendrik Ballerstedt, Jan Gerritse, J T C GrotenhuisAbstract:The biodegradation of a mixture of benzene, toluene, Ethylbenzene, xylene, (BTEX) and methyl-tert-butyl ether (MTBE) was studied in soil microcosms. Soil inoculation with the toluene-metabolising fungusCladophialophora sp. strain T1 was evaluated in sterile and non-sterile soil. Induction of biodegradation capacity following BTEX addition was faster in the soil native microflora than in axenic soil cultures of the fungus. Toluene, Ethylbenzenes, and the xylenes were metabolized by the fungus but biodegradation of benzene required the activity of the indigenous soil microorganisms. MTBE was not biodegraded under the tested environmental conditions. Biodegradation profiles were also examined under two pH conditions after a long term exposure to BTEX. At neutral conditions the presence of the fungus had little effect on the intrinsic soil biodegradation capacity. At an acidic pH, however, the activity of the indigenous degraders was inhibited and the presence of Cladophialophora sp. increased significantly the biodegradation rates of toluene and Ethylbenzene. Comparison of the BTEX biodegradation rates measured in soil batches combining presence and absence of indigenous degraders and the fungal inoculum indicated that no severe antagonism occurred between the indigenous bacteria and Cladophialophora sp. The presence of the fungal inoculum at the end of the experiments was confirmed by PCR-TGGE analysis of small subunits of 18S rDNA.
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substrate interactions during the biodegradation of benzene toluene Ethylbenzene and xylene btex hydrocarbons by the fungus cladophialophora sp strain t1
Applied and Environmental Microbiology, 2002Co-Authors: Francesc X Prenafetaboldu, J T C Grotenhuis, Jacques Vervoort, J W Van GroenestijnAbstract:The soil fungus Cladophialophora sp. strain T1 (= ATCC MYA-2335) was capable of growth on a model water-soluble fraction of gasoline that contained all six BTEX components (benzene, toluene, Ethylbenzene, and the xylene isomers). Benzene was not metabolized, but the alkylated benzenes (toluene, Ethylbenzene, and xylenes) were degraded by a combination of assimilation and cometabolism. Toluene and Ethylbenzene were used as sources of carbon and energy, whereas the xylenes were cometabolized to different extents. o-Xylene and m-xylene were converted to phthalates as end metabolites; p-xylene was not degraded in complex BTEX mixtures but, in combination with toluene, appeared to be mineralized. The metabolic profiles and the inhibitory nature of the substrate interactions indicated that toluene, Ethylbenzene, and xylene were degraded at the side chain by the same monooxygenase enzyme. Our findings suggest that soil fungi could contribute significantly to bioremediation of BTEX pollution.
Francesc X Prenafetaboldu - One of the best experts on this subject based on the ideXlab platform.
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bioremediation of btex hydrocarbons effect of soil inoculation with the toluene growing fungus cladophialophora sp strain t1
Biodegradation, 2004Co-Authors: Francesc X Prenafetaboldu, Hendrik Ballerstedt, Jan Gerritse, J T C GrotenhuisAbstract:The biodegradation of a mixture of benzene, toluene, Ethylbenzene, xylene, (BTEX) and methyl-tert-butyl ether (MTBE) was studied in soil microcosms. Soil inoculation with the toluene-metabolising fungusCladophialophora sp. strain T1 was evaluated in sterile and non-sterile soil. Induction of biodegradation capacity following BTEX addition was faster in the soil native microflora than in axenic soil cultures of the fungus. Toluene, Ethylbenzenes, and the xylenes were metabolized by the fungus but biodegradation of benzene required the activity of the indigenous soil microorganisms. MTBE was not biodegraded under the tested environmental conditions. Biodegradation profiles were also examined under two pH conditions after a long term exposure to BTEX. At neutral conditions the presence of the fungus had little effect on the intrinsic soil biodegradation capacity. At an acidic pH, however, the activity of the indigenous degraders was inhibited and the presence of Cladophialophora sp. increased significantly the biodegradation rates of toluene and Ethylbenzene. Comparison of the BTEX biodegradation rates measured in soil batches combining presence and absence of indigenous degraders and the fungal inoculum indicated that no severe antagonism occurred between the indigenous bacteria and Cladophialophora sp. The presence of the fungal inoculum at the end of the experiments was confirmed by PCR-TGGE analysis of small subunits of 18S rDNA.
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substrate interactions during the biodegradation of benzene toluene Ethylbenzene and xylene btex hydrocarbons by the fungus cladophialophora sp strain t1
Applied and Environmental Microbiology, 2002Co-Authors: Francesc X Prenafetaboldu, J T C Grotenhuis, Jacques Vervoort, J W Van GroenestijnAbstract:The soil fungus Cladophialophora sp. strain T1 (= ATCC MYA-2335) was capable of growth on a model water-soluble fraction of gasoline that contained all six BTEX components (benzene, toluene, Ethylbenzene, and the xylene isomers). Benzene was not metabolized, but the alkylated benzenes (toluene, Ethylbenzene, and xylenes) were degraded by a combination of assimilation and cometabolism. Toluene and Ethylbenzene were used as sources of carbon and energy, whereas the xylenes were cometabolized to different extents. o-Xylene and m-xylene were converted to phthalates as end metabolites; p-xylene was not degraded in complex BTEX mixtures but, in combination with toluene, appeared to be mineralized. The metabolic profiles and the inhibitory nature of the substrate interactions indicated that toluene, Ethylbenzene, and xylene were degraded at the side chain by the same monooxygenase enzyme. Our findings suggest that soil fungi could contribute significantly to bioremediation of BTEX pollution.
Qixing Zhou - One of the best experts on this subject based on the ideXlab platform.
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behavioral alteration and dna damage of freshwater snail bellamya aeruginosa stressed by Ethylbenzene and its tissue residue
Ecotoxicology and Environmental Safety, 2012Co-Authors: Shimei Zheng, Qixing Zhou, Jie Gao, Hongxia Xiong, Cuihong ChenAbstract:To study the sublethal effects induced by Ethylbenzene and the capability of a freshwater gastropod Bellamya aeruginosa to take up and depurate Ethylbenzene, the snail was subjected to two treatments, a 23-day exposure period followed by a 17-day depuration period. Behavioral alteration, namely retraction response, was observed during the exposure period, and the proportion of retracted snails increased under each treatment as the exposure time prolonged but there was no linear relationship between the retracted proportion and the exposure dose. Such behavioral alteration was probably due to the disturbance of membrane permeability stressed by Ethylbenzene. Ethylbenzene uptake in unretracted snails was greater than in retracted snails, while the depuration abilities in the two different responses of snails had no significant difference from each other. Because of the limited capability of snails to detoxify Ethylbenzene, the depuration was mainly through a slow excretion process and therefore Ethylbenzene was still present in the tissue of snail after 17-day depuration. DNA damage was induced significantly in snails exposed to Ethylbenzene, and the levels of DNA damage showed positive time-response and dose-response relationships, and moreover the levels of DNA damage had no difference between the two different responses of snails. There was no linear relationship between the level of DNA damage and the amount of residual Ethylbenzene in tissue, which may be related to the adaptation mechanism in snail. Overall, the results suggest that the snail has high capability to take up Ethylbenzene and low ability to depurate it, and Ethylbenzene has potential genotoxicity to snail.
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toxic effects of hydrilla verticillata exposed to toluene Ethylbenzene and xylene and safety assessment for protecting aquatic macrophytes
Chemosphere, 2011Co-Authors: Sha Yan, Qixing ZhouAbstract:Little information is available about the toxicity of toluene, Ethylbenzene and xylene acting on macrophytes, and their toxicity data are rarely used in regulation and criteria decisions. The results extended the knowledge on toxic effects of toluene, Ethylbenzene and xylene on aquatic plants. The responses of Hydrilla verticillata to these pollutants were investigated. Chlorophyll levels, lipid peroxidation, and antioxidant enzymes (superoxide dismutase and guaiacol peroxidase) showed diverse responses at different concentrations of toluene, Ethylbenzene and xylene. The linear regression analyses were performed respectively, suggesting the concentrations of toluene, Ethylbenzene and xylene expected to protect aquatic macrophytes were 7.30 mg L⁻¹, 1.15 mg L⁻¹ and 2.36 mg L⁻¹, respectively. This study emphasized that aquatic plants are also sensitive to organic pollutants as fishes and zooplanktons, indicating that macrophytes could be helpful in predicting the toxicity of these pollutants and should be considered in regulation and criteria decisions for aquatic environment protection.
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The effects of photosynthetic pigments on Hydrilla verticillata and Vallisneria spiralis induced by toluene, Ethylbenzene and xylene
2011 International Symposium on Water Resource and Environmental Protection, 2011Co-Authors: Qixing ZhouAbstract:Effects of toluene, Ethylbenzene and xylene on the contents of chlorophylls (a and b) were investigated in Hydrilla verticillata and Vallisneria spiralis. Hydrilla verticillata exhibited increases at lowest concentrations, while the loss in chlorophyll contents at higher chemicals concentrations occurred. Linear regression analyses were performed. IC10 values were 7.30mg/L, 1.15mg/L and 2.36mg/L for toluene, Ethylbenzene and xylene. Chlorophylls contents of Vallisneria spiralis showed the erratic reduces at all concentrations of pollutants except three sampling points, showing photosynthesis of Vallisneria spiralis was negatively affected because of the toxicity of pollutants. The results indicated that the mechanism of the toxicity induced by toluene, Ethylbenzene and xylene may have some differences, and Hydrilla verticillata was more suitable to be used in toxicity tests.
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oxidative stress and dna damage in the earthworm eisenia fetida induced by toluene Ethylbenzene and xylene
Ecotoxicology, 2010Co-Authors: Qixing Zhou, Luxi DongAbstract:Superoxide dismutase (SOD), guaiacol peroxidase (POD), catalase (CAT), and the comet assay (SCGE) were used as biomarkers to evaluate the oxidative stress and genotoxicity of toluene, Ethylbenzene and xylene in earthworms (Eisenia fetida). The results indicated that the exposure of the three pollutants caused a stress response of the three enzymes, an approximate bell-shaped change (a tendency of inducement firstly and then inhibition with increasing concentrations of the pollutants) was mostly found. The three enzymes tested differed in their sensitivity to different pollutants. While the activity of POD was not significantly changed within the concentration range, the concentration thresholds for significant (P < 0.05) responses to toluene based on SOD and CAT were 5 mg kg−1, respectively. Similarly, the concentration thresholds for significant (P < 0.05) responses to Ethylbenzene based on CAT and POD were 10 and 5 mg kg−1, respectively, while the activity of SOD was not significantly changed within the concentration range. Significant responses to xylene based on CAT and POD were 5 mg kg−1, respectively, while the activity of SOD was significantly (P < 0.05) induced at 10 mg kg−1. The SCGE assay results showed that these three pollutants could significantly (P < 0.01) induce DNA damage in earthworms and the clear dose-dependent relationships were displayed, indicating potential genotoxic effects of toluene, Ethylbenzene, and xylene on E. fetida. The inducement of DNA damage may be attributed to the oxidative attack of toluene, Ethylbenzene, and xylene. Toluene seemed to be more genotoxic as it could induce the higher extent of DNA damage than Ethylbenzene and xylene. The results suggest that the SCGE assay of earthworms is simple and efficient for diagnosing the genotoxicity of pollutants in terrestrial environment.