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Organic Substrates (organic + substrate)
Selected Abstracts4-Benzylpyridinium Fluorochromate: An Efficient and Selective Oxidant for Organic Substrates.CHEMINFORM, Issue 18 2007Beytiye Oezguen Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] ChemInform Abstract: Unexpected Catalytic Activity of N-Hydroxyphthalimide Combined with Some Co-Catalysts in Oxidation of Organic Substrates by Dioxygen.CHEMINFORM, Issue 38 2001P. J. Figiel Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Anaerobic degradation of benzene by a marine sulfate-reducing enrichment culture, and cell hybridization of the dominant phylotypeENVIRONMENTAL MICROBIOLOGY, Issue 1 2008Florin Musat Summary The anaerobic biodegradation of benzene, a common constituent of petroleum and one of the least reactive aromatic hydrocarbons, is insufficiently understood with respect to the involved microorganisms and their metabolism. To study these aspects, sulfate-reducing bacteria were enriched with benzene as sole organic substrate using marine sediment as inoculum. Repeated subcultivation yielded a sediment-free enrichment culture constituted of mostly oval-shaped cells and showing benzene-dependent sulfate reduction and growth under strictly anoxic conditions. Amplification and sequencing of 16S rRNA genes from progressively diluted culture samples revealed an abundant phylotype; this was closely related to a clade of Deltaproteobacteria that includes sulfate-reducing bacteria able to degrade naphthalene or other aromatic hydrocarbons. Cell hybridization with two specifically designed 16S rRNA-targeted fluorescent oligonucleotide probes showed that the retrieved phylotype accounted for more than 85% of the cells detectable via DAPI staining (general cell staining) in the enrichment culture. The result suggests that the detected dominant phylotype is the ,candidate species' responsible for the anaerobic degradation of benzene. Quantitative growth experiments revealed complete oxidation of benzene with stoichiometric coupling to the reduction of sulfate to sulfide. Suspensions of benzene-grown cells did not show metabolic activity towards phenol or toluene. This observation suggests that benzene degradation by the enriched sulfate-reducing bacteria does not proceed via anaerobic hydroxylation (mediated through dehydrogenation) to free phenol or methylation to toluene, respectively, which are formerly proposed alternative mechanisms for benzene activation. [source] Synthesis of para -Amino Benzoic Acid,TiO2 Hybrid Nanostructures of Controlled Functionality by an Aqueous One-Step ProcessEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2008Raed Rahal Abstract In situ amino acid surface-modified TiO2 nanoparticle syntheses were performed by a simple one-pot hydrolysis of heteroleptic titanium alkoxide [Ti(OiPr)3(O2CC6H4NH2)]m in water with NnBu4Br. This process allowed precise control of the surface grafting rate by varying the amount of precursors and provided highly functionalized nanomaterials. Their compositions and microstructures were determined by C, H and N elemental analyses, TGA-MS, 13C CP-MAS NMR, XRD, TEM, BET, Raleigh diffusion, FTIR, Raman, XPS and UV/Vis experiments. The results indicated that (i) the aggregation rate increased with an increase in the loading of the organic substrate and (ii) the amino acid is chemisorbed as a carboxylate group onto the TiO2 nanoparticles, which leads to a strong interaction between the amino acid and the TiO2 nanoparticle and good stability of these hybrids. Applications of low-aggregated nanomaterials were demonstrated as efficient protection additive against UVA + UVB radiations.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Field-scale 13C-labeling of phospholipid fatty acids (PLFA) and dissolved inorganic carbon: tracing acetate assimilation and mineralization in a petroleum hydrocarbon-contaminated aquiferFEMS MICROBIOLOGY ECOLOGY, Issue 3 2002Silvina A. Pombo Abstract This study was conducted to determine the feasibility of labeling phospholipid-derived fatty acids (PLFA) of an active microbial population with a 13C-labeled organic substrate in the denitrifying zone of a petroleum hydrocarbon-contaminated aquifer during a single-well push-pull test. Anoxic test solution was prepared from 500 l of groundwater with addition of 0.5 mM Br, as a conservative tracer, 0.5 mM NO3,, and 0.25 mM [2- 13C]acetate. At 4, 23 and 46 h after injection, 1000 l of test solution/groundwater mixture were sequentially extracted. During injection and extraction phases we measured Br,, NO3, and acetate concentrations, characterized the microbial community structure by PLFA and fluorescent in situ hybridization (FISH) analyses, and determined 13C/12C ratios in dissolved inorganic carbon (DIC) and PLFA. Computed first-order rate coefficients were 0.63±0.08 day,1 for NO3, and 0.70±0.05 day,1 for acetate consumption. Significant 13C incorporation in DIC and PLFA was detected as early as 4 h after injection. At 46 h we measured ,13C values of up to 5614, in certain PLFA (especially monounsaturated fatty acids), and up to 59.8, in extracted DIC. Profiles of enriched PLFA and FISH analysis suggested the presence of active denitrifiers. Our results demonstrate the applicability of 13C labeling of PLFA and DIC in combination with FISH to link microbial structure and activities at the field scale during a push-pull test. [source] Fluorous Surface-Active Distannoxane CatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Akihiro Orita Abstract Fluorous distannoxanes (XRf2SnOSnRf2X)2,n,H2O (Rf=C6F13C2H4) (1: X=C8F17SO3, n=10; 4: X=Cl, n=0) (1) catalyze the Mukaiyama aldol reaction and the allylation of aldehydes with tetraallyltin at room temperature in fluorous/organic biphasic solvent systems, in which the reactions proceed more rapidly than in a single organic or fluorous solvent. Due to the unique surface activity of 1, the catalyst, organic substrate(s), and reagent(s) are distributed in both organic and fluorous phases to facilitate smooth reactions. Upon dilution with toluene after the reaction, the catalyst concentrates to the fluorous phase, while the organic substances migrate to the organic phase to effect facile catalyst recovery and recycling. By virtue of such a unique solvophilicity, a new version of fluorous biphase technology has been developed. [source] Efficient Biocatalytic Cleavage and Recovery of Organic Substrates Supported on Soluble PolymersADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2007Dario Pasini Abstract The applicability of novel solution-phase supports in combination with enzymes for biocatalytic transformations is reported. Ex novo designed styrene-based copolymers, bearing a phenylacetic residue in variable loadings and linked as a pendant group to the macromolecular backbone, through a spacer of variable length, have been synthesized and characterized. These derivatives are compatible and can be used as soluble supports in combination with immobilized penicillin G acylase (PGA , EC 3.5.1.11) for the biocatalytic cleavage of the covalently anchored organic substrate in quantitative yields, in water or water/dimethylformamide solvent mixtures, with recovery of the immobilized enzyme with negligible losses in activity. [source] A Mechanistic Study on Alcohol Oxidations with Oxygen Catalysed by TPAP-Doped Ormosils in Supercritical Carbon DioxideADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2005Sandro Campestrini Abstract The heterogeneous oxidation of various alcohols with oxygen catalysed by TPAP-doped ormosils in scCO2 at 75,°C and 22.0,MPa has been studied in detail. Sol-gel segregation of TPAP into the inner porosity of an organically modified silica (ormosil) xerogel along with the use of a reaction medium which does not dissolve the catalyst, prevents aggregation of oxidation-inactive ruthenium derivatives without the need of chemical tethering. Thus, at least 140 TONs may be obtained in the oxidation of primary alcohols with the formation of aldehydes as sole reaction products. Investigation of the oxidation mechanism shows that the catalytic process exhibits a first-order dependence on the amount of catalyst, a fractional order on the alcohol concentration and a negative order for oxygen pressures higher than 0.2,bar. Evidence is presented for an associative oxidation mechanism simultaneously involving TPAP, organic substrate and oxygen. [source] Effects of influent C/N ratio, C/P ratio and volumetric exchange ratio on biological phosphorus removal in UniFed SBR processJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2008Chen-hong Zhao Abstract BACKGROUND: UniFed SBR is a novel process that can achieve high levels of nitrogen and phosphorus removal simultaneously in a simple single SBR tank. In this study, effects of influent C/N ratio, influent C/P ratio and volumetric exchange ratio on biological phosphorus removal in UniFed SBR process were investigated in a lab-scale UniFed apparatus treating real domestic wastewater. RESULTS: The results showed that phosphorus removal efficiency increased as C/N ratio increased from 27% at 2.8 to 88% at 5.7. For C/N ratios 6.5 and above, complete phosphorus removal could be achieved. When C/N ratios and volumetric exchange ratio were fixed at 6 and 33%, respectively, phosphorus removal efficiency remained at 100% for C/P ratios higher than 33; effluent phosphate concentration was below the detection limit. For C/P ratios lower than 33, phosphorus removal efficiency decreased linearly with C/P ratio. Under the same influent C/N ratio and C/P ratio, the following factors all contributed to better phosphorus removal performance: greater volumetric exchange ratio; more organic substrate for PAOs to utilize, less inhibition by NOx, of phosphorus release during the feed/decant period; more PHB synthesized; and more aerobic phosphate uptake. CONCLUSION: High influent C/N ratio, high C/P ratio and high volumetric exchange ratio were beneficial to phosphorus removal in this process. Copyright © 2008 Society of Chemical Industry [source] A proteomic view of the facultatively chemolithoautotrophic lifestyle of Ralstonia eutropha H16PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 22 2009Edward Schwartz Abstract Ralstonia eutropha H16 is an H2 -oxidizing, facultative chemolithoautotroph. Using 2-DE in conjunction with peptide mass spectrometry we have cataloged the soluble proteins of this bacterium during growth on different substrates: (i) H2 and CO2, (ii) succinate and (iii) glycerol. The first and second conditions represent purely lithoautotrophic and purely organoheterotrophic nutrition, respectively. The third growth regime permits formation of the H2 -oxidizing and CO2 -fixing systems concomitant to utilization of an organic substrate, thus enabling mixotrophic growth. The latter type of nutrition is probably the relevant one with respect to the situation faced by the organism in its natural habitats, i.e. soil and mud. Aside from the hydrogenase and Calvin-cycle enzymes, the protein inventories of the H2 -CO2 - and succinate-grown cells did not reveal major qualitative differences. The protein complement of the glycerol-grown cells resembled that of the lithoautotrophic cells. Phosphoenolpyruvate (PEP) carboxykinase was present under all three growth conditions, whereas PEP carboxylase was not detectable, supporting earlier findings that PEP carboxykinase is alone responsible for the anaplerotic production of oxaloacetate from PEP. The elevated levels of oxidative stress proteins in the glycerol-grown cells point to a significant challenge by ROS under these conditions. The results reported here are in agreement with earlier physiological and enzymological studies indicating that R. eutropha H16 has a heterotrophic core metabolism onto which the functions of lithoautotrophy have been grafted. [source] Photosynthetic microbial fuel cells with positive light responseBIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009Yongjin Zou Abstract The current study introduces an aerobic single-chamber photosynthetic microbial fuel cell (PMFC). Evaluation of PMFC performance using naturally growing fresh-water photosynthetic biofilm revealed a weak positive light response, that is, an increase in cell voltage upon illumination. When the PMFC anodes were coated with electrically conductive polymers, the rate of voltage increased and the amplitude of the light response improved significantly. The rapid immediate positive response to light was consistent with a mechanism postulating that the photosynthetic electron-transfer chain is the source of the electrons harvested on the anode surface. This mechanism is fundamentally different from the one exploited in previously designed anaerobic microbial fuel cells (MFCs), sediment MFCs, or anaerobic PMFCs, where the electrons are derived from the respiratory electron-transfer chain. The power densities produced in PMFCs were substantially lower than those that are currently reported for conventional MFC (0.95,mW/m2 for polyaniline-coated and 1.3,mW/m2 for polypyrrole-coated anodes). However, the PMFC did not depend on an organic substrate as an energy source and was powered only by light energy. Its operation was CO2 -neutral and did not require buffers or exogenous electron transfer shuttles. Biotechnol. Bioeng. 2009; 104: 939,946. © 2009 Wiley Periodicals, Inc. [source] Ecophysiology of a group of uncultured Gammaproteobacterial glycogen-accumulating organisms in full-scale enhanced biological phosphorus removal wastewater treatment plantsENVIRONMENTAL MICROBIOLOGY, Issue 3 2006Yunhong Kong Summary The presence of glycogen-accumulating organisms (GAOs) in enhanced biological phosphorus removal (EBPR) plants can seriously deteriorate the biological P-removal by out-competing the polyphosphate-accumulating organisms (PAOs). In this study, uncultured putative GAOs (the GB group, belonging to the Gammaproteobacteria) were investigated in detail in 12 full-scale EBPR plants. Fluorescence in situ hybridization (FISH) revealed that the biovolume of the GB bacteria constituted 2,6% of total bacterial biovolume. At least six different subgroups of the GB bacteria were found, and the number of dominant subgroups present in each plant varied between one and five. Ecophysiological investigations using microautoradiography in combination with FISH showed that, under aerobic or anaerobic conditions, all subgroups of the GB bacteria could take up acetate, pyruvate, propionate and some amino acids, while some subgroups in addition could take up formate and thymidine. Glucose, ethanol, butyrate and several other organic substrates were not taken up. Glycolysis was essential for the anaerobic uptake of organic substrates. Polyhydroxyalkanoates (PHA) but not polyphosphate (polyP) granules were detected in all GB bacterial cells. Polyhydroxyalkanoate formation after anaerobic uptake of acetate was confirmed by measuring the increase in fluorescence intensity of PHA granules inside GB bacterial cells after Nile blue staining. One GB subgroup was possibly able to denitrify, and several others were able to reduce nitrate to nitrite. PAOs were also enumerated by FISH in the same treatment plants. Rhodocyclus -related PAOs and Actinobacteria -related PAOs constituted up to 7% and 29% of total bacterial biovolume respectively. Rhodocyclus -related PAOs always coexisted with the GB bacteria and showed many physiological similarities. Factors of importance for the competition between the three groups of important bacteria in EBPR plants are discussed. [source] Isolation and properties of methanesulfonate-degrading Afipia felis from Antarctica and comparison with other strains of A. felisENVIRONMENTAL MICROBIOLOGY, Issue 1 2005S. Azra Moosvi Summary Three novel strains of methylotrophic Afipia felis were isolated from several locations on Signy Island, Antarctica, and a fourth from estuary sediment from the River Douro, Portugal. They were identified as strains of the ,-2 proteobacterium A. felis by 16S rRNA gene sequence, analysis., Two, strains, tested, were, shown to contain the fdxA gene, diagnostic for A. felis. All strains grew with methanesulfonate (and two strains with dimethylsulfone) as sole carbon substrate. Growth on methanesulfonate required methanesulfonate monooxygenase (MSAMO), using NADH as the reductant and stimulated by reduced flavin nucleotides and Fe(II). Polymerase chain reaction amplification of DNA from an Antarctic strain showed a typical msmA gene for the ,-hydroxylase of MSAMO, and both Antarctic and Portuguese strains contained mxaF, the methanol dehydrogenase large subunit gene. This is the first report of methanesulfonate-degrading bacteria from the Antarctic and of methylotrophy in Afipia, and the first description of any bacterium able to use both methanesulfonate and dimethylsulfone. In contrast, the type strain of A. felis DSM 7326T was not methylotrophic, but grew in defined mineral medium with a wide range of single simple organic substrates. Free-living Afipia strains occurring widely in the natural environment may be significant as methylotrophs, degrading C1 -sulfur compounds, including the recalcitrant organosulfur compound methanesulfonate. [source] In situ studies of the phylogeny and physiology of filamentous bacteria with attached growthENVIRONMENTAL MICROBIOLOGY, Issue 7 2002Trine Rolighed Thomsen Summary Among the filamentous bacteria occasionally causing bulking problems in activated sludge treatment plants, three morphotypes with attached microbial growth are common, Eikelboom Type 0041, Type 1851 and Type 1701. A better knowledge of the phylogeny and physiology of these filamentous bacteria is necessary in order to develop control strategies for bulking. In this study we have used a combination of fluorescence in situ hybridization (FISH) and microautoradiography (MAR) to investigate the identity and in situ physiology of the Type 0041-morphotype and its attached bacteria in two wastewater treatment plants. Identification and enumeration of Type 0041 using group-specific 16S rRNA-targeted FISH probes revealed that approximately 15% of the filaments hybridized with a gene probe specific for the TM7 group, a recently recognized major lineage in the bacterial domain. All other filaments morphologically identified as Type 0041 only hybridized to the general bacterial EUB338-probe, indicating that they probably do not belong to commonly isolated bacterial phyla such as the Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes, for which group-specific probes were used. The phylogenetic heterogeneity of Type 0041 again highlights the inadequacy of a morphology-based classification system. Like the filaments, most of the attached microbial cells were not identified beyond their affiliation to the Bacteria using the group-specific FISH probes. However, several different bacterial phyla were represented in the identified fraction suggesting that the attached microorganisms are phylogenetically diverse. The study of the in situ physiology of Type 0041 using MAR-FISH revealed that both the filaments and the attached bacteria on Type 0041 were versatile in the use of organic substrates and electron acceptors. It was observed that all Type 0041 could consume glucose, but none of the filaments were able to consume acetate under any conditions tested, in contrast to some of the attached bacteria. No significant physiological differences were found between TM7,positive and TM7,negative Type 0041 filaments, and only minor differences were observed between the two treatment plants tested. These are the first data on the physiology of the almost entirely uncharacterized TM7 phylum and show that TM7 filamentous bacteria can uptake carbon substrates under aerobic and anaerobic conditions. [source] Dielectric Properties of a Printed Sol,Gel Matrix Composite,ADVANCED ENGINEERING MATERIALS, Issue 5 2010Tobias Lehnert Low temperature processable materials with high dielectric constants are required for application on flexible organic substrates, for example, in printed electronics. To date, mainly organic polymers with embedded functional particles have been investigated for this purpose. For the first time, we present a printable dielectric composite material composed of ferroelectric high permittivity particles (BaTiO3) bonded by a mainly inorganic sol,gel derived network. The exemplary optimization of the properties by varying the sol,gel precursor illustrates the potential of sol,gel chemistry for printable functional materials. An operational gravure printed capacitor including printed silver electrodes is presented. The measured dielectric constants are among the highest reported in literature for low temperature cured films with moderate dissipation factors. Besides these promising dielectric properties, this composite film shows a ferroelectric response. [source] MIOR: an individual-based model for simulating the spatial patterns of soil organic matter microbial decompositionEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 5 2007D. Masse Summary An individual-based model, called MIOR, was designed to assess hypotheses on the effect of the spatial distribution of organic matter and microbial decomposers on soil carbon and nitrogen dynamics. Two main types of object were defined to represent the decomposers and the soil organic substrates. All these objects were positioned in a 3D space. The exchange of carbon and nitrogen between these various entities was simulated. Two scenarios were tested according to the degrees of clustering of organic matter and of microorganisms. The results of simulations highlighted the effect of the ratio of accessible organic carbon to microbial carbon on the dynamics of microbial biomass and CO2 release. This ratio was determined by the number of contacts between one object representing the microbial decomposers and the surrounding objects representing the organic substrates. MIOR: modèle individu-centré de simulation de la distribution spatiale des processus microbiens de la décomposition des matières organiques dans les sols Résumé Un modèle individu-centré, appelé MIOR, a été conçu pour tester les hypothèses concernant les effets de la distribution spatiale des matières organiques et des microdécomposeurs dans les sols sur la dynamique du carbone et de l'azote minéral. Deux principaux types d'objets ont été définis représentant les microorganismes décomposeurs et les substrats organiques. Ces objets sont positionnés dans une espace à trois dimensions. Les échanges de carbone et d'azote entre ces deux entités sont simulés. Deux scénarios sont testés selon des niveaux d'agrégation des microorganismes et celui des matières organiques. Les résultats des simulations mettent en avant l'importance de la quantité de carbone organique accessible par unité de carbone microbien sur la dynamique de la biomasse microbienne et du CO2 dégagé. Cette quantité est déterminée par le nombre de contacts entre un objet représentant des microdécomposeurs et des objets qui l'entourent représentant les substrats organiques. [source] Ecophysiology of the filamentous Alphaproteobacterium Meganema perideroedes in activated sludgeFEMS MICROBIOLOGY ECOLOGY, Issue 1 2005Caroline Kragelund Abstract A comprehensive study of the ecophysiology of the filamentous Meganema perideroedes affiliated to the Alphaproteobacteria, possessing a "Nostocoida limicola Type II" filamentous morphology was conducted. This morphotype often causes serious bulking problems in activated sludge wastewater treatment plants, and hardly anything is known about its physiology. The study was carried out by applying a suite of in situ methods in an industrial activated sludge treatment plant with excessive growth of this species. The experiments revealed a very versatile organism able to take up a large variety of organic substrates under aerobic conditions. It had a remarkably high storage capacity forming polyhydroxyalkanoates from most substrates tested. When nitrate was present as e-acceptor, the number of substrates to be consumed by M. perideroedes was more restricted compared to aerobic conditions. With nitrite as e-acceptor, only acetate and glucose among the substrates tested could be assimilated and used for storage and possibly growth. This indicated that M. perideroedes might be able to denitrify under certain conditions, which is unusual for filamentous bacteria in activated sludge. No substrate uptake or storage was seen under anaerobic conditions. M. perideroedes was relatively hydrophobic, compared to other filamentous bacteria and microcolonies present in the sludge, indicating the presence of a hydrophobic sheath. Several excreted surface-associated exoenzymes were detected in the sludge, but M. perideroedes never showed any activity, except once after a breakdown in the production facility. This confirmed that M. perideroedes mainly grows on soluble substrates. Based on the studies of the ecophysiology of M. perideroedes, potential control strategies are suggested. [source] A kinetic perspective on extracellular electron transfer by anode-respiring bacteriaFEMS MICROBIOLOGY REVIEWS, Issue 1 2010César I. Torres Abstract In microbial fuel cells and electrolysis cells (MXCs), anode-respiring bacteria (ARB) oxidize organic substrates to produce electrical current. In order to develop an electrical current, ARB must transfer electrons to a solid anode through extracellular electron transfer (EET). ARB use various EET mechanisms to transfer electrons to the anode, including direct contact through outer-membrane proteins, diffusion of soluble electron shuttles, and electron transport through solid components of the extracellular biofilm matrix. In this review, we perform a novel kinetic analysis of each EET mechanism by analyzing the results available in the literature. Our goal is to evaluate how well each EET mechanism can produce a high current density (>10 A m,2) without a large anode potential loss (less than a few hundred millivolts), which are feasibility goals of MXCs. Direct contact of ARB to the anode cannot achieve high current densities due to the limited number of cells that can come in direct contact with the anode. Slow diffusive flux of electron shuttles at commonly observed concentrations limits current generation and results in high potential losses, as has been observed experimentally. Only electron transport through a solid conductive matrix can explain observations of high current densities and low anode potential losses. Thus, a study of the biological components that create a solid conductive matrix is of critical importance for understanding the function of ARB. [source] Energetics of overall metabolic reactions of thermophilic and hyperthermophilic Archaea and BacteriaFEMS MICROBIOLOGY REVIEWS, Issue 2 2001Jan P. Amend Abstract Thermophilic and hyperthermophilic Archaea and Bacteria have been isolated from marine hydrothermal systems, heated sediments, continental solfataras, hot springs, water heaters, and industrial waste. They catalyze a tremendous array of widely varying metabolic processes. As determined in the laboratory, electron donors in thermophilic and hyperthermophilic microbial redox reactions include H2, Fe2+, H2S, S, S2O32,, S4O62,, sulfide minerals, CH4, various mono-, di-, and hydroxy-carboxylic acids, alcohols, amino acids, and complex organic substrates; electron acceptors include O2, Fe3+, CO2, CO, NO3,, NO2,, NO, N2O, SO42,, SO32,, S2O32,, and S. Although many assimilatory and dissimilatory metabolic reactions have been identified for these groups of microorganisms, little attention has been paid to the energetics of these reactions. In this review, standard molal Gibbs free energies (,Gr°) as a function of temperature to 200°C are tabulated for 370 organic and inorganic redox, disproportionation, dissociation, hydrolysis, and solubility reactions directly or indirectly involved in microbial metabolism. To calculate values of ,Gr° for these and countless other reactions, the apparent standard molal Gibbs free energies of formation (,G°) at temperatures to 200°C are given for 307 solids, liquids, gases, and aqueous solutes. It is shown that values of ,Gr° for many microbially mediated reactions are highly temperature dependent, and that adopting values determined at 25°C for systems at elevated temperatures introduces significant and unnecessary errors. The metabolic processes considered here involve compounds that belong to the following chemical systems: H,O, H,O,N, H,O,S, H,O,N,S, H,O,Cinorganic, H,O,C, H,O,N,C, H,O,S,C, H,O,N,S,Camino acids, H,O,S,C,metals/minerals, and H,O,P. For four metabolic reactions of particular interest in thermophily and hyperthermophily (knallgas reaction, anaerobic sulfur and nitrate reduction, and autotrophic methanogenesis), values of the overall Gibbs free energy (,Gr) as a function of temperature are calculated for a wide range of chemical compositions likely to be present in near-surface and deep hydrothermal and geothermal systems. [source] Bacterial metabolism in small temperate streams under contemporary and future climatesFRESHWATER BIOLOGY, Issue 12 2007KAJ SAND-JENSEN Summary 1. We examined the detailed temperature dependence (0,40 °C) of bacterial metabolism associated with fine sediment particles from three Danish lowland streams to test if temperature dependence varied between sites, seasons and quality of organic matter and to evaluate possible consequences of global warming. 2. A modified Arrhenius model with reversible denaturation at high temperatures could account for the temperature dependence of bacterial metabolism and the beginning of saturation above 35 °C and it was superior to the unmodified Arrhenius model. Both models overestimated respiration rates at very low temperatures (<5 °C), whereas Ratkowsky's model , the square root of respiration , provided an excellent linear fit between 0 and 30 °C. 3. There were no indications of differences in temperature dependence among samples dominated by slowly or easily degradable organic substrates. Optimum temperature, apparent minimum temperature, Q10 -values for 0,40 °C and activation energies of bacterial respiration were independent of season, stream site and degradability of organic matter. 4. Q10 -values of bacterial respiration declined significantly with temperature (e.g. 3.31 for 5,15 °C and 1.43 for 25,35 °C) and were independent of site and season. Q10 -values of bacterial production behaved similarly, but were significantly lower than Q10 -values of respiration implying that bacterial growth efficiency declined with temperature. 5. A regional warming scenario for 2071,2100 (IPCC A2) predicted that mean annual temperatures will increase by 3.5 °C in the air and 2.2,4.3 °C in the streams compared with the control scenario for 1961,1990. Temperature is expected to rise more in cool groundwater-fed forest springs than in open, summer-warm streams. Mean annual bacterial respiration is estimated to increase by 26,63% and production by 18,41% among streams assuming that established metabolism,temperature relationships and organic substrate availability remain the same. To improve predictions of future ecosystem behaviour, we further require coupled models of temperature, hydrology, organic production and decomposition. [source] Temperature dependence of Fe(III) and sulfate reduction rates and its effect on growth and composition of bacterial enrichments from an acidic pit lake neutralization experimentGEOBIOLOGY, Issue 4 2005J. MEIER ABSTRACT Microbial Fe(III) and sulfate reduction are important electron transport processes in acidic pit lakes and stimulation by the addition of organic substrates is a strategy to remove acidity, iron and sulfate. This principle was applied in a pilot-scale enclosure in pit lake 111 (Brandenburg, Germany). Because seasonal and spatial variation of temperature may affect the performance of in situ experiments considerably, the influence of temperature on Fe(III) and sulfate reduction was investigated in surface sediments from the enclosure in the range of 4,28 °C. Potential Fe(III) reduction and sulfate reduction rates increased exponentially with temperature, and the effect was quantified in terms of the apparent activation energy Ea measuring 42,46 kJ mol,1 and 52 kJ mol,1, respectively. Relatively high respiration rates at 4 °C and relatively low Q10 values (,2) indicated that microbial communities were well adapted to low temperatures. In order to evaluate the effect of temperature on growth and enrichment of iron and sulfate-reducing bacterial populations, MPN (Most Probable Number) dilution series were performed in media selecting for the different bacterial groups. While the temperature response of specific growth rates of acidophilic iron reducers showed mesophilic characteristics, the relatively high specific growth rates of sulfate reducers at the lowest incubation temperature indicated the presence of moderate psychrophilic bacteria. In contrast, the low cell numbers and low specific growth rates of neutrophilic iron reducers obtained in dilution cultures suggest that these populations play a less significant role in Fe and S cycling in these sediments. SSCP (Single-Strand Conformation Polymorphism) or DGGE (Denaturing Gradient Gel Electrophoresis) fingerprinting based on 16S rRNA genes of Bacteria indicated different bacterial populations in the MPN dilution series exhibiting different temperature ranges for growth. [source] Catalytic Hydroxylation in Biphasic Systems using CYP102A1 MutantsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2005Steffen Abstract Cytochrome P450 monooxygenases are biocatalysts that hydroxylate or epoxidise a wide range of hydrophobic organic substrates. Their technical application is, however, limited to a small number of whole-cell processes. The use of the isolated P450 enzymes is believed to be impractical due to their low stability, stoichiometric need of the expensive cofactor NAD(P)H and low solubility of most substrates in aqueous media. We investigated the behaviour of an isolated bacterial monooxygenase (mutants of CYP102A1) in a biphasic reaction system supported by cofactor recycling with the NADP+ -dependent formate dehydrogenase from Pseudomonas sp 101. Using this experimental set-up cyclohexane, octane and myristic acid were hydroxylated. To reduce the process costs a novel NADH-dependent mutant of CYP102A1 was designed. For recycling of NADH an NAD+ -dependent FDH was used. The stability of the monooxygenase mutants under the reaction conditions in the biphasic system was quite high as revealed by total turnover numbers of up to 12,850 in the NADPH-dependent cyclohexane hydroxylation and up to 30,000 in the NADH-dependent myristic acid oxidation. [source] A gemini amphiphilic phase transfer catalyst for dark singlet oxygenationJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 7-8 2008Cédric Borde Abstract A new gemini surfactant phase transfer catalyst, namely diethyl-ether-,,,-bis-(dimethyldodecylammonium molybdate) codified as 12-EO-12-Mo, was prepared by anion exchange from the analogous gemini dichloride (12-EO-12-Cl2). The physico-chemical properties of these compounds such as Krafft temperature, critical micelle concentration, surface activity and binary water-surfactant behavior were compared and the influence of the molybdate counterion was examined. Though both compounds are highly hydrophilic, the cmc of 12-EO-12-Mo (0.4,mmol L,1) is about five times lower than of its dichloride analogue (2.2,mmol L,1). Moreover, 12-EO-12-Mo exhibits an additional cubic liquid crystal phase between 53 and 64,wt%. The usefulness of 12-EO-12-Mo as an amphiphilic phase transfer catalyst for the dark singlet oxygenation was demonstrated with the peroxidation of two typical organic substrates: ,-terpinene which reacts with 1O2 according to a [4,+,2] cycloaddition and the less reactive ,-citronellol, which provides two hydroperoxides according to the ene-reaction. 12-EO-12-Mo provides a simple reaction medium with only three components for the preparative peroxidation of hydrophobic substrates by chemically generated singlet oxygen. Copyright © 2008 John Wiley & Sons, Ltd. [source] Mass spectrometric characterization of high-valent metal-oxo, -peroxo and -peroxy intermediates of relevance in oxidation processesMASS SPECTROMETRY REVIEWS, Issue 5 2006Olga Bortolini Abstract The coupling of mass spectrometry with ionization techniques like electrospray ionization (ESI) or matrix-assisted matrix-assisted laser desorption-ionization (MALDI) offers many advantages over other well-established spectroscopic techniques employed for the investigation of intermediates or short-lived species in condensed-phase. In this review we describe some of the applications of mass spectrometry, in particular of ESI-MS to the detection and characterization of high-valent metal-oxo, -peroxo and -peroxy derivatives, crucial intermediates in the oxyfunctionalization of organic substrates. In addition, by utilizing gas-phase ion-molecule reactions and MS/MS experiments, information on the intrinsic reactivity of the short-lived intermediates may be obtained. The combined use of ESI-MS in association with other spectroscopic techniques and theoretical calculations is discussed as well. © 2006 Wiley Periodicals, Inc. [source] A new dawn , the ecological genetics of mycorrhizal fungiNEW PHYTOLOGIST, Issue 2 2000D. LEE TAYLOR Many human activities, such as ore mining and smeltering, sewage sludge treatment and fossil fuel consumption, result in toxic soil concentrations of ,heavy metals' (Al, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Ti, Zn and others) (Gadd, 1993). There are also natural soils, such as serpentine, with levels of heavy metals that inhibit or preclude the growth of many plants and soil micro-organisms. However, certain plants and microorganisms do grow in these metalliferous sites. Understanding the physiology, ecology and evolution of tolerance to elevated soil metal concentrations is important in an applied setting, and is also of interest in theoretical biology. Applied importance relates to the improvement of forest health in areas subject to increasing pollution, rehabilitation of severely polluted sites by phytostabilization of metals, and metal removal using hyperaccumulating plants (Krämer, 2000; Ernst, 2000). Areas of theoretical interest include the evolution of local adaptation (Sork et al., 1993) and how it is shaped by the combined influences of natural selection, gene flow and genetic architecture, as well as metal influences on various species interactions (Pollard, 2000). A paper appears on pages 367,379 in this issue by Jan Colpaert and coworkers which adroitly combines the disparate fields of physiology, genetics and ecology to answer several outstanding questions concerning heavy metal tolerance in mycorrhizal fungi. Mycorrhizal fungi, which interact mutualistically with the majority of plant species, are well known for improving the P status of their hosts (Smith & Read, 1997). Some mycorrhizal fungi are also able to mobilize N and P from organic substrates and to provide plants with improved micronutrient and water acquisition, pathogen resistance, and a variety of other benefits (Smith & Read, 1997). One of these additional benefits is the amelioration of toxicity in metalliferous soils. [source] Fabrication of free-standing ultrathin films of porous metal-organic frameworks by liquid-phase epitaxy and subsequent delaminationPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 8-9 2010Masih Darbandi Abstract In this work we describe an approach to fabricate MOF (metal-organic framework) platelets with predefined shapes and well-defined thicknesses. The process is based on growing thin, highly oriented and ordered MOF films by selective liquid-phase epitaxy on prestructured organic substrates. In a second step, the MOF platelets are delaminated employing a lift-off process. The freestanding MOF platelets were characterized with TEM and SEM, which showed no evidence of fracture or deformation of the delaminated shapes. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Pseudomonas putida KT2440 responds specifically to chlorophenoxy herbicides and their initial metabolitesPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 11 2006Dirk Benndorf Dr. Abstract Pseudomonas putida,KT2440 is often used as a model to investigate toxicity mechanisms and adaptation to hazardous chemicals in bacteria. The objective of this paper was to test the impact of the chlorophenoxy herbicides 2,4-dichlorophenoxyacetic acid,(2,4-D) and 2-(2,4-dichlorophenoxy)propanoic acid,(DCPP) and their metabolites 2,4-dichlorophenol,(DCP) and 3,5-dichlorocatechol,(DCC), on protein expression patterns and physiological parameters. Both approaches showed that DCC has a different mode of action and induces different responses than DCPP, 2,4-D and DCP. DCC was the most toxic compound and was active as an uncoupler of oxidative phosphorylation. It repressed the synthesis of ferric uptake regulator (Fur)-dependent proteins, e.g. fumarase,C and L -ornithine N5-oxygenase, which are involved in oxidative stress response and iron uptake. DCPP, 2,4-D and DCP were less toxic than DCC. They disturbed oxidative phosphorylation to a lesser extent by a yet unknown mechanism. Furthermore, they repressed enzymes of energy-consuming biosynthetic pathways and induced membrane transporters for organic substrates. A TolC homologue component of multidrug resistance transporters was found to be induced, which is probably involved in the removal of lipophilic compounds from membranes. [source] Critical assessment of the applicability of gas chromatography-combustion-isotope ratio mass spectrometry to determine amino sugar dynamics in soilRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2009Charlotte Decock Amino sugars in soils have been used as markers of microbial necromass and to determine the relative contribution of bacterial and fungal residues to soil organic matter. However, little is known about the dynamics of amino sugars in soil. This is partly because of a lack of adequate techniques to determine ,turnover rates' of amino sugars in soil. We conducted an incubation experiment where 13C-labeled organic substrates of different quality were added to a sandy soil. The objectives were to evaluate the applicability of compound-specific stable isotope analysis via gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) for the determination of 13C amino sugars and to demonstrate amino sugar dynamics in soil. We found total analytical errors between 0.8 and 2.6, for the ,13C-values of the soil amino sugars as a result of the required ,13C-corrections for isotopic alterations due to derivatization, isotopic fractionation and analytical conditions. Furthermore, the ,13C-values of internal standards in samples determined via GC-C-IRMS deviated considerably from the ,13C-values of the pure compounds determined via elemental analyzer IRMS (with a variation of 9 to 10, between the first and third quartile among all samples). This questions the applicability of GC-C-IRMS for soil amino sugar analysis. Liquid chromatography-combustion-IRMS (LC-C-IRMS) might be a promising alternative since derivatization, one of the main sources of error when using GC-C-IRMS, is eliminated from the procedure. The high 13C-enrichment of the substrate allowed for the detection of very high 13C-labels in soil amino sugars after 1 week of incubation, while no significant differences in amino sugar concentrations over time and across treatments were observed. This suggests steady-state conditions upon substrate addition, i.e. amino sugar formation equalled amino sugar decomposition. Furthermore, higher quality substrates seemed to favor the production of fungal-derived amino sugars. Copyright © 2009 John Wiley & Sons, Ltd. [source] Restoration effort, habitat mosaics, and macroinvertebrates , does channel form determine community composition?AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2009Sonja C. Jähnig Abstract 1.In certain lower mountainous regions of Germany multiple-channel streams constitute the reference condition for stream restoration and conservation efforts. An increasing number of restoration projects re-establish such stream sections, but their impact on macroinvertebrate communities remains vague and needs further elaboration. 2.Seven pairs of single- and multiple-channel sections of mountain rivers were compared in terms of hydromorphology and macroinvertebrate communities. The stream sections were characterized by 16 hydromorphological metrics at various scales, e.g. shore length, channel feature or substrate diversity, flow variability and substrate coverage. Macroinvertebrate data were obtained from 140 substrate-specific samples, which were combined to form representative communities for each section. Community data were subject to similarity and cluster analyses. Thirty-five metrics were calculated with the taxa lists, including number of taxa, abundance, feeding type, habitat and current preferences. 3.Bray,Curtis similarity was very high (69,77%) between communities of single- and multiple-channel sections. Biological metrics were correlated with hydromorphological parameters. Mean Spearman rank r was 0.59 (absolute values). The biological metrics percentage of the community preferring submerged vegetation, being grazers and scrapers or active filter feeders, percentage of epipotamal preference and the percentage of current preference (rheo- to limnophil and rheobiont) were significantly correlated with hydromorphological parameters. 4.Differences between stream sections can be attributed to single taxa occurring only in either the single- or multiple-channel sections. These exclusive taxa were mainly found on organic substrates such as living parts of terrestrial plants, large wood, coarse particulate organic matter (CPOM) and mud. Reasons for high similarity of macroinvertebrate communities from single- or multiple-channel sections are discussed, including the influence of large-scale catchment pressures, length of restored sections and lack of potential re-colonizers. Copyright © 2008 John Wiley & Sons, Ltd. [source] Functional expression and stabilization of horseradish peroxidase by directed evolution in Saccharomyces cerevisiaeBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2001Birgit Morawski Abstract Biotechnology applications of horseradish peroxidase (HRP) would benefit from access to tailor-made variants with greater specific activity, lower Km for peroxide, and higher thermostability. Starting with a mutant that is functionally expressed in Saccharomyces cerevisiae, we used random mutagenesis, recombination, and screening to identify HRP-C mutants that are more active and stable to incubation in hydrogen peroxide at 50°C. A single mutation (N175S) in the HRP active site was found to improve thermal stability. Introducing this mutation into an HRP variant evolved for higher activity yielded HRP 13A7-N175S, whose half-life at 60°C and pH 7.0 is three times that of wild-type (recombinant) HRP and a commercially available HRP preparation from Sigma (St. Louis, MO). The variant is also more stable in the presence of H2O2, SDS, salts (NaCl and urea), and at different pH values. Furthermore, this variant is more active towards a variety of small organic substrates frequently used in diagnostic applications. Site-directed mutagenesis to replace each of the four methionine residues in HRP (M83, M181, M281, M284) with isoleucine revealed no mutation that significantly increased the enzyme's stability to hydrogen peroxide. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 76: 99,107, 2001. [source] | |||||||||||||||||||