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排序方式: 共有429条查询结果,搜索用时 15 毫秒
71.
Stoichiometry of soil enzyme activity at global scale 总被引:27,自引:0,他引:27
Sinsabaugh RL Lauber CL Weintraub MN Ahmed B Allison SD Crenshaw C Contosta AR Cusack D Frey S Gallo ME Gartner TB Hobbie SE Holland K Keeler BL Powers JS Stursova M Takacs-Vesbach C Waldrop MP Wallenstein MD Zak DR Zeglin LH 《Ecology letters》2008,11(11):1252-1264
Extracellular enzymes are the proximate agents of organic matter decomposition and measures of these activities can be used as indicators of microbial nutrient demand. We conducted a global-scale meta-analysis of the seven-most widely measured soil enzyme activities, using data from 40 ecosystems. The activities of beta-1,4-glucosidase, cellobiohydrolase, beta-1,4-N-acetylglucosaminidase and phosphatase g(-1) soil increased with organic matter concentration; leucine aminopeptidase, phenol oxidase and peroxidase activities showed no relationship. All activities were significantly related to soil pH. Specific activities, i.e. activity g(-1) soil organic matter, also varied in relation to soil pH for all enzymes. Relationships with mean annual temperature (MAT) and precipitation (MAP) were generally weak. For hydrolases, ratios of specific C, N and P acquisition activities converged on 1 : 1 : 1 but across ecosystems, the ratio of C : P acquisition was inversely related to MAP and MAT while the ratio of C : N acquisition increased with MAP. Oxidative activities were more variable than hydrolytic activities and increased with soil pH. Our analyses indicate that the enzymatic potential for hydrolyzing the labile components of soil organic matter is tied to substrate availability, soil pH and the stoichiometry of microbial nutrient demand. The enzymatic potential for oxidizing the recalcitrant fractions of soil organic material, which is a proximate control on soil organic matter accumulation, is most strongly related to soil pH. These trends provide insight into the biogeochemical processes that create global patterns in ecological stoichiometry and organic matter storage. 相似文献
72.
A comprehensive model was developed to describe the kinetics of the laccase‐catalyzed oxidation of phenol that incorporates enzyme kinetics, enzyme inactivation, variable reaction stoichiometry between substrate and oxygen, and oxygen mass‐transfer. The model was calibrated and validated against data obtained from experiments conducted in an open system, which allowed oxygen to transfer from air to the reacting mixture and phenol conversion to approach completion. Inactivation of laccase was observed over the course of the reaction and was found to be dependent on the rate of substrate transformation. A single kinetic expression was sufficient to describe laccase inactivation arising from interaction with reacting species over time. Excellent agreement was found between model predictions of phenol and oxygen concentrations and experimental data over time for a wide range of initial substrate concentrations and enzyme activities. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 相似文献
73.
Leonardo Tavares Salgado Leonardo Paes Cinelli Nathan Bessa Viana Rodrigo Tomazetto de Carvalho Paulo Antônio De Souza Mourão Valéria Laneuville Teixeira Marcos Farina And Gilberto Menezes Amado Filho 《Journal of phycology》2009,45(1):193-202
The interaction between phenolic substances (PS) and alginates (ALG) has been suggested to play a role in the structure of the cell walls of brown seaweeds. However, no clear evidence for this interaction was reported. Vanadium bromoperoxidase (VBPO) has been proposed as a possible catalyst for the binding of PS to ALG. In this work, we studied the interaction between PS and ALG from brown algae using size exclusion chromatography (SEC) and optical tweezers microscopy. The analysis by SEC revealed that ALG forms a high‐molecular‐weight complex with PS. To study the formation of this molecular complex, we investigated the in vitro interaction of purified ALG from Fucus vesiculosus L. with purified PS from Padina gymnospora (Kütz.) Sond., in the presence or absence of VBPO. The interaction between PS and ALG only occurred when VBPO was added, indicating that the enzyme is essential for the binding process. The interaction of these molecules led to a reduction in ALG viscosity. We propose that VBPO promotes the binding of PS molecules to the ALG uronic acids residues, and we also suggest that PS are components of the brown algal cell walls. 相似文献
74.
Nuri Azbar Fatih Tutuk Tugba Keskin 《International biodeterioration & biodegradation》2009,63(6):690-698
The primary objective of this study was to evaluate the performance of a 20 l lab scale anaerobic hybrid reactor (AHR) combining sludge blanket in the lower part and filter in the upper part under varying organic loading rates (OLRs) in order to study biodegradation of olive mill effluent (OME). For this purpose, some parameters, such as total phenols, effluent chemical oxygen demand (COD), suspended solids (SS), volatile fatty acids (VFAs), and pH in the influent and effluent, and removal efficiencies for those parameters (except pH) were continuously monitored throughout the experimental period of 477 days. Eleven different organic loadings between 0.45 and 32 kg COD m−3 day−1 were imposed by either varying influent COD or hydraulic retention time (HRT). The results demonstrated that the AHR reactor could tolerate high influent COD concentrations. Removal efficiencies for the studied pollution parameters were found to be as follows: COD, 50–94%; total phenol, 39–80%; color, 0–54%; and suspended solids, 19–87%. The levels of VFAs in the effluent, which was principally acetate, butyrate, iso-butyrate, and propionate, varied between 10 and 2005 mg l−1 depending upon OLRs. A COD removal efficiency of 90% could be achieved as long as OLR is kept at a level of less than 10 kg COD m−3 day−1. However, a secondary treatment unit for polishing purposes is necessary to comply with receiving media discharge standards. 相似文献
75.
This article describes the employment of a novel p-phenol derivative, 4-(1,2,4-triazol-1-yl)phenol (TRP), as a highly potent signal enhancer of the luminol-hydrogen peroxide (H2O2)-horseradish peroxidase (HRP) chemiluminescence (CL) system. The CL reaction conditions were optimized, and the enhancement characteristics of TRP were compared with those of p-iodophenol (PIP). TRP produced a strong enhancement of the CL with the effect of prolonging the light emission. The developed system was then applied to the determination of H2O2 with immobilized HRP using magnetic beads as a solid support. The linear range for H2O2 was 2.0 × 10−6 to 1.0 × 10−3 M. The detection limit for H2O2 was 2.0 × 10−6 M. The proposed sensor was applied successfully to the determination of H2O2 in rainwater. 相似文献
76.
C. Abdul JALEEL Changxing ZHAO Sedghi MOHAMED Hameed Jasim AL-JUBURI Helal Ragab MOUSSA M. GOMATHINAYAGAM R. PANNEERSELVAM 《生物学前沿》2009,4(4)
Changes in the sucrose metabolism of Cur-cuma longa L. plants were studied under treatment with different triazole compounds viz., triadimefon (TDM) and propiconazole (PCZ). Plants were treated with TDM at 15 mg/L and PCZ at 10 mg/L separately by soil drenching on 80, 110, and 140 days after planting (DAP). The plants were harvested randomly on 90, 120, and 150DAP to determine the effect of both the triazoles on sucrose metabolizing enzymes and phenol content. The sucrose metabolism was studied by analyzing sucrose metaboliz-ing enzymes like sucrose synthase and sucrose phosphate synthase. All the analyses were assayed in leaves and tubers of both control and treated plants. It was found that both of the triazole compounds had profound effects on these parameters. 相似文献
77.
紫果猕猴桃嫩枝多酚氧化酶活性与总酚含量变化 总被引:1,自引:0,他引:1
采用紫果猕猴桃嫩枝和叶柄为试材,分析全年中植株多酚氧化酶(PPO)活性和总酚含量的变化规律。结果表明,紫果猕猴桃植株PPO活性的最适pH为7.0;最佳底物为邻苯二酚,且浓度为0.16 mol/L;最佳温度为25 ℃。紫果猕猴桃植株生长期的PPO活性明显高于休眠期,植株总酚含量在4月、5月、9 月达最低。 相似文献
78.
Neuropeptide Y (NPY) has been reported to be a potent anti-inflammatory peptide with ability to directly modulate activity of granulocytes and macrophages. The present study aimed to correlate the effects of NPY in vivo on lipopolysaccharide-induced air-pouch exudates cells and in vitro on peripheral blood leukocytes functions. The role of different Y receptors was examined using NPY-related peptides and antagonists with diverse subtype specificity and selectivity for Y receptors. Y1, Y2 and Y5 receptors were detected on air-pouch exudates cells (flow cytometry) and peripheral blood granulocytes (immunocitochemistry). NPY in vivo reduced inflammatory cells accumulation into the air pouch, and decreased their adherence and phagocytic capacity via Y2/Y5 and Y1/Y2 receptors, respectively. Quite the opposite, NPY in vitro potentiated adhesiveness and phagocytosis of peripheral blood granulocytes and monocytes by activating Y1 receptor. The differences between in vivo and in vitro effects of NPY on rat inflammatory cells functions are mostly due to dipeptidyl peptidase 4 activity. In addition, suppressive effect of NPY in vivo is highly dependent on the local microenvironment, peptide truncation and specific Y receptors interplay. 相似文献
79.
大豆(Glycine max)含硫氨基酸合成途径中的酶基因是含硫氨基酸组分的重要调控基因,发掘相关酶基因对高含硫氨基酸分子育种具有重要意义。文章采用大豆物理与遗传整合图谱,通过BioMercator2.1将113个含硫氨基酸合成途径酶基因及33个控制含硫氨基酸含量的QTL整合到遗传图谱Consensus Map 4.0上,依据酶基因位点与QTL的一致性以及QTL的效应值,初步筛选到16个与含硫氨基酸合成相关的候选基因。通过生物信息学方法对候选基因进行拷贝数、SNP、表达谱等分析,鉴定到12个相关酶基因,分别位于D1a、M、A2、K和G等8个连锁群上。生物信息学分析显示这些基因所在QTL可解释含硫氨基酸遗传变异的6.0%~38.5%,其中9个基因的间接效应值超过10%。12个相关酶基因参与含硫氨基酸代谢的重要途径,且多在子叶、花中高丰度表达,存在丰富的SNP。这些基因可作为候选基因进行功能标记开发,将为大豆分子设计育种奠定基础。 相似文献
80.
Intercellular communication in bacteria (quorum sensing, QS) is an important phenomenon in disease dissemination and pathogenesis, which controls biofilm formation also. This study reports the anti-QS and anti-biofilm efficacy of seaweed Gracilaria gracilis associated Vibrio alginolyticus G16 against Serratia marcescens. Purification and mass spectrometric analysis revealed the active principle as phenol, 2,4-bis(1,1-dimethylethyl) [PD]. PD affected the QS regulated virulence factor production in S. marcescens and resulted in a significant (p < 0.05) reduction in biofilm (85%), protease (41.9%), haemolysin (69.9%), lipase (84.3%), prodigiosin (84.5%) and extracellular polysaccharide (84.62%) secretion without hampering growth, as evidenced by XTT [2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] assay. qPCR analysis confirmed the down-regulation of the fimA, fimC, flhD and bsmA genes involved in biofilm formation. Apart from biofilm inhibition and disruption, PD increased the susceptibility of S. marcescens to gentamicin when administered synergistically, which opens another avenue for combinatorial therapy where PD can be used to enhance the efficacy of conventional antibiotics. 相似文献