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1.
Malachite green (MG) was decolorized by laccase (LacA) of white-rot fungus Cerrena sp. with strong decolorizing ability. Decolorization conditions were optimized with response surface methodology. A highly significant quadratic model was developed to investigate MG decolorization with LacA, and the maximum MG decolorization ratio of 91.6% was predicted under the conditions of 2.8 U mL-1 LacA, 109.9 mg L-1 MG and decolorization for 172.4 min. Kinetic studies revealed the Km and kcat values of LacA toward MG were 781.9 mM and 9.5 s-1, respectively. UV–visible spectra confirmed degradation of MG, and the degradation mechanism was explored with liquid chromatography–mass spectrometry (LC-MS) analysis. Based on the LC-MS spectra of degradation products, LacA catalyzed MG degradation via two simultaneous pathways. In addition, the phytotoxicity of MG, in terms of inhibition on seed germination and seedling root elongation of Nicotiana tabacum and Lactuca sativa, was reduced after laccase treatment. These results suggest that laccase of Cerrena was effective in decolorizing MG and promising in bioremediation of wastewater in food and aquaculture industries.  相似文献   

2.
Week-old wheat seedlings absorbed at least 40% NO3 from NaNO3 when preloaded with K+ than when preloaded with Na+ or Ca2+. Cultures of Triticum vulgare L. cv. Arthur were grown for 5 days on 0.2 mm CaSO4, pretreated for 48 hours with either 1 mm CaSO4, K2SO4, or Na2SO4, and then transferred to 1 mm NaNO3. All solutions contained 0.2 mm CaSO4. Shoots of K+-preloaded plants accumulated three times more NO3 than shoots of the other two treatments. Initially, the K+-preloaded plants contained 10-fold more malate than either Na+- or Ca2+-preloaded seedlings. During the 48-hour treatment with NaNO3, malate in both roots and shoots of the K+-preloaded seedlings decreased. Seedlings preloaded with K+ reduced 25% more NO3 than those preloaded with either Na+ or Ca2+. These experiments indicate that K+ enhanced NO3 uptake and reduction even though the absorption of K+ and NO3 were separated in time. Xylem exudate of K+-pretreated plants contained roughly equivalent concentrations of K+ and NO3, but exudate from Na+ and Ca2+-pretreated plants contained two to four times more NO3 than K+. Therefore K+ is not an obligatory counterion for NO3 transport in xylem.  相似文献   

3.
Soybeans (Glycine max L. Merr., cv Kingsoy) were grown on media containing NO3 or urea. The enrichments of shoots in K+, NO3, and total reduced N (Nr), relative to that in Ca2+, were compared to the ratios K+/Ca2+,NO3/Ca2+, and Nr/Ca2+ in the xylem saps, to estimate the cycling of K+, and Nr. The net production of carboxylates (R) was estimated from the difference between the sums of the main cations and inorganic anions. The estimate for shoots was compared to the theoretical production of R associated with NO3 assimilation in these organs, and the difference was attributed to export of R to roots. The net exchange rates of H+ and OH between the medium and roots were monitored. The shoots were the site of more than 90% of total NO3 reduction, and Nr was cycling through the plants at a high rate. Alkalinization of the medium by NO3-fed plants was interrupted by stem girdling, and not restored by glucose addition to the medium. It was concluded that the majority of the base excreted in NO3 medium originated from R produced in the shoots, and transported to the roots together with K+. As expected, cycling of K+ and reduced N was favoured by NO3 nutrition as compared to urea nutrition.  相似文献   

4.
Group V (GV) phospholipase A2 (PLA2) is a member of the family of secreted PLA2 (sPLA2) enzymes. This enzyme has been identified in several organs, including the kidney. However, the physiologic role of GV sPLA2 in the maintenance of renal function remains unclear. We used mice lacking the gene encoding GV sPLA2 (Pla2g5−/−) and wild-type breeding pairs in the experiments. Mice were individually housed in metabolic cages and 48-h urine was collected for biochemical assays. Kidney samples were evaluated for glomerular morphology, renal fibrosis, and expression/activity of the (Na+ + K+)-ATPase α1 subunit. We observed that plasma creatinine levels were increased in Pla2g5−/− mice following by a decrease in creatinine clearance. The levels of urinary protein were higher in Pla2g5−/− mice than in the control group. Markers of tubular integrity and function such as γ-glutamyl transpeptidase, lactate dehydrogenase, and sodium excretion fraction (FENa+) were also increased in Pla2g5−/− mice. The increased FENa+ observed in Pla2g5−/− mice was correlated to alterations in cortical (Na+ + K+) ATPase activity/ expression. In addition, the kidney from Pla2g5−/− mice showed accumulation of matrix in corticomedullary glomeruli and tubulointerstitial fibrosis. These data suggest GV sPLA2 is involved in the maintenance of tubular cell function and integrity, promoting sodium retention through increased cortical (Na+ + K+)-ATPase expression and activity.  相似文献   

5.
To clarify the kinetic characteristics and ionic requirements of the tonoplast H+-translocating inorganic pyrophosphatase (H+-PPiase), PPi hydrolysis and PPi-dependent H+ transport were studied in tonoplast vesicles isolated from leaf mesophyll tissue of Kalanchoë daigremontiana Hamet et Perrier de la Bâthie. The tonoplast H+-PPiase showed an absolute requirement for a monovalent cation and exhibited hyperbolic kinetics with respect to cation concentration. H+-PPiase activity was maximal in the presence of K+ (K50 approximately 3 millimolar), with PPi-dependent H+ transport being more selective for K+ than PPi hydrolysis. When assayed in the presence of 50 millimolar KCl at fixed PPi concentrations, H+-PPiase activity showed sigmoidal kinetics with respect to total Mg concentration, reflecting a requirement for a Mg/PPi complex as substrate and free Mg2+ for activation. At saturating concentrations of free Mg2+, H+-PPiase activity exhibited Michaelis-Menten kinetics towards MgPPi2− but not Mg2PPi, demonstrating that MgPPi2− was the true substrate of the enzyme. The apparent Km (MgPPi2−) for PPi hydrolysis (17 micromolar) was significantly higher than that for PPi-dependent H+ transport (7 micromolar). Free Mg2+ was shown to be an allosteric activator of the H+-PPiase, with Hill coefficients of 2.5 for PPi hydrolysis and 2.7 for PPi-dependent H+ transport. Half-maximal H+-PPiase activity occurred at a free Mg2+ concentration of 1.1 millimolar, which lies within the range of accepted values for cytosolic Mg2+. In contrast, cytosolic concentrations of K+ and MgPPi2− appear to be saturating for H+-PPiase activity. We propose that one function of the H+-PPiase may be to act as an ancillary enzyme that maintains the proton-motive force across the vacuolar membrane when the activity of the tonoplast H+-ATPase is restricted by substrate availability. As ATP levels decline in the cytosol, free Mg2+ would be released from the MgATP2− complex, thereby activating the tonoplast H+-PPiase.  相似文献   

6.
The investigations were focussed on the question as to whether roots of intact maize plants (Zea mays L. cv Blizzard) release protons into deionized H2O. Plants in the six to seven leaf stage depressed the pH of deionized H2O from 6 to about 4.8 during an experimental period of 4 hours. Only one-third of the protons released could be ascribed to the solvation of CO2 in H2O. The main counter anions released were Cl, NO3, and SO42−. At low temperature (2°C), the H+ release was virtually blocked while a relatively high amount of K+ was released. The presence of K+, Na+, Ca2+, and Mg2+ in the external solution increased the H+ secretion significantly. Addition of vanadate to the outer medium inhibited the H+ release while fusicoccin had a stimulating effect. Substituting the nutrient solution of deionized H2O resulted in a substantial increase of the membrane potential difference from −120 to −190 millivolts. The experimental results support the conclusion that the H+ release by roots of intact maize plants is an active process driven by a plasmalemmalocated ATPase. Since the net H+ release was not associated with a net uptake of K+, it is unlikely to originate from a K+/H+ antiport.  相似文献   

7.
Sealed microsomal vesicles were prepared from corn (Zea mays, Crow Single Cross Hybrid WF9-Mo17) roots by centrifugation of a 10,000 to 80,000g microsomal fraction onto a 10% dextran T-70 cushion. The Mg2+-ATPase activity of the sealed vesicles was stimulated by Cl and NH4+ and by ionophores and protonophores such as 2 micromolar gramicidin or 10 micromolar carbonyl cyanide p-trifluoromethoxyphenyl hydrazone (FCCP). The ionophore-stimulated ATPase activity had a broad pH optimum with a maximum at pH 6.5. The ATPase was inhibited by NO3, was insensitive to K+, and was not inhibited by 100 micromolar vanadate or by 1 millimolar azide.

Quenching of quinacrine fluorescence was used to measure ATP-dependent acidification of the intravesicular volume. Quenching required Mg2+, was stimulated by Cl, inhibited by NO3, was insensitive to monovalent cations, was unaffected by 200 micromolar vanadate, and was abolished by 2 micromolar gramicidin or 10 micromolar FCCP. Activity was highly specific for ATP. The ionophore-stimulated ATPase and ATP-dependent fluorescence quench both required a divalent cation (Mg2+ ≥ Mn2+ > Co2+) and were inhibited by high concentrations of Ca2+. The similarity of the ionophore-stimulated ATPase and quinacrine quench and the responses of the two to ions suggest that both represent the activity of the same ATP-dependent proton pump. The characteristics of the proton-translocating ATPase differed from those of the mitochondrial F1F0-ATPase and from those of the K+-stimulated ATPase of corn root plasma membranes, and resembled those of the tonoplast ATPase.

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8.
《Process Biochemistry》2014,49(7):1196-1204
Laccase from a tree legume, Leucaena leucocephala, was purified to homogeneity using a quick two-step procedure: alginate bead entrapment and celite adsorption chromatography. Laccase was purified 110.6-fold with an overall recovery of 51.0% and a specific activity of 58.5 units/mg. The purified laccase was found to be a heterodimer (∼220 kDa), containing two subunits of 100 and 120 kDa. The affinity of laccase was found to be highest for catechol and lowest for hydroquinone, however, highest Kcat and Kcat/Km were obtained for hydroquinone. Purified laccase exhibited pH and temperature optima of 7.0 and 80 °C, respectively. Mn2+, Cd2+, Fe2+, Cu2+ and Na+ activated laccase while Ca2+ treatment increased laccase activity up to 3 mM, beyond which it inhibited laccase. Co2+, Hg2+, DTT, SDS and EDTA showed an inhibition of laccase activity. The Leucaena laccase was found to be fairly tolerant to organic solvents; upon exposure for 1 h individually to 50% (v/v) each of ethanol, DMF, DMSO and benzene, more than 50% of the activity was retained, while in the presence of 50% (v/v) each of methanol, isopropanol and chloroform, a 40% residual activity was observed. The purified laccase efficiently decolorized synthetic dyes such as indigocarmine and congo red in the absence of any redox mediator.  相似文献   

9.
Activation of Na+,HCO3 cotransport in vascular smooth muscle cells (VSMCs) contributes to intracellular pH (pHi) control during artery contraction, but the signaling pathways involved have been unknown. We investigated whether physical and functional interactions between the Na+,HCO3 cotransporter NBCn1 (slc4a7) and the Ca2+/calmodulin-activated serine/threonine phosphatase calcineurin exist and play a role for pHi control in VSMCs. Using a yeast two-hybrid screen, we found that splice cassette II from the N terminus of NBCn1 interacts with calcineurin Aβ. When cassette II was truncated or mutated to disrupt the putative calcineurin binding motif PTVVIH, the interaction was abolished. Native NBCn1 and calcineurin Aβ co-immunoprecipitated from A7r5 rat VSMCs. A peptide (acetyl-DDIPTVVIH-amide), which mimics the putative calcineurin binding motif, inhibited the co-immunoprecipitation whereas a mutated peptide (acetyl-DDIATAVAA-amide) did not. Na+,HCO3 cotransport activity was investigated in VSMCs of mesenteric arteries after an NH4+ prepulse. During depolarization with 50 mm extracellular K+ to raise intracellular [Ca2+], Na+,HCO3 cotransport activity was inhibited 20–30% by calcineurin inhibitors (FK506 and cyclosporine A). FK506 did not affect Na+,HCO3 cotransport activity in VSMCs when cytosolic [Ca2+] was lowered by buffering, nor did it disrupt binding between NBCn1 and calcineurin Aβ. FK506 augmented the intracellular acidification of VSMCs during norepinephrine-induced artery contractions. No physical or functional interactions between calcineurin Aβ and the Na+/H+ exchanger NHE1 were observed in VSMCs. In conclusion, we demonstrate a physical interaction between calcineurin Aβ and cassette II of NBCn1. Intracellular Ca2+ activates Na+,HCO3 cotransport activity in VSMCs in a calcineurin-dependent manner which is important for protection against intracellular acidification.  相似文献   

10.
An investigation was conducted into the feasibility of using enzymically isolated protoplasts from suspension-cultured cells of Nicotiana glutinosa L. to study ion transport. Transport of K+ (86Rb), 36Cl, H232PO4 and 45Ca2+ from 1 millimolar salt solutions was determined after separation of intact protoplasts from nonabsorbed tracers by centrifugation through a Ficoll step gradient. Influx of K+, Cl, and H2PO4 measured over a 30-minute period was reduced (up to 99%) by respiratory inhibitors such as 5 micrograms per milliliter oligomycin, 0.1 millimolar dinitrophenol, 0.1 millimolar cyanide, or N2 gas. In contrast, Ca2+ influx was not tightly coupled to respiratory energy production. The influx of K+ was highest between pH 6.5 and 7.5 whereas the influx of H2PO4 and Cl was greatest between pH 4.5 and 5.5. Influx of K+ and Cl was maximal at 35 and 45 C, respectively, and was almost completely inhibited below 10 C. Fusicoccin (0.01 millimolar) stimulated K+ influx by more than 200% but had no effect on the influx of either Cl or H2PO4. Apparent H+ efflux, as measured by decrease in solution pH, was enhanced by K+, stimulated further by 0.01 millimolar fusicoccin, and inhibited by 0.1 millimolar dinitrophenol or 5 micrograms per milliliter oligomycin. The measured ionic fluxes into protoplasts were similar to those obtained with intact cultured cells. The results indicate that enzymic removal of the cell wall produced no significant alteration in the transport properties of the protoplast, and that it is feasible to use isolated protoplasts for studies on ion transport.  相似文献   

11.
Mg2+-ATP-dependent H+-translocation has been studied in membrane vesicles derived from the roots of Gossypium hirsutum L. var. Acala San Jose 2. Establishment of a positive membrane potential was followed by measuring SCN accumulation; establishment of ΔpH across the vesicle membranes by measuring quinacrine fluorescence quenching. High specificity for ATP was shown, and H+-translocation was oligomycin stable. The pH profile for H+-translocation showed an optimum at 5.5. The relationship between SCN accumulation and ATP concentration was approximately Michaelian; the apparent Km was 0.7 millimolar. K-2-(N-morpholino)ethanesulfonic acid strongly promoted ATP-dependent SCN uptake (up to 180% stimulation). The effect was not given by Na-Mes. Carbonyl cyanide p-trifluoromethoxyphenylhydrazone totally inhibited SCN accumulation, both in the presence and absence of K-2(N-morpholino)ethanesulfonic acid. Vanadate at 200 micromolar inhibited SCN uptake by about 10 to 40% in the absence of K+, but more strongly in its presence (about 60%). NO3 at 100 millimolar inhibited initial rate of quinacrine quenching by about 25%. The NO3 insensitive fraction was activated by K+; and inhibited by 200 micromolar vanadate to about 40%, provided K+ was present. Saline conditions during the growth of the plants had no appreciable effect on the observed characteristics of H+-translocation.  相似文献   

12.
The Na,K-ATPase α2 isoform is the predominant Na,K-ATPase in adult skeletal muscle and the sole Na,K-ATPase in the transverse tubules (T-tubules). In quiescent muscles, the α2 isozyme operates substantially below its maximal transport capacity. Unlike the α1 isoform, the α2 isoform is not required for maintaining resting ion gradients or the resting membrane potential, canonical roles of the Na,K-ATPase in most other cells. However, α2 activity is stimulated immediately upon the start of contraction and, in working muscles, its contribution is crucial to maintaining excitation and resisting fatigue. Here, we show that α2 activity is determined in part by the K+ concentration in the T-tubules, through its K+ substrate affinity. Apparent K+ affinity was determined from measurements of the K1/2 for K+ activation of pump current in intact, voltage-clamped mouse flexor digitorum brevis muscle fibers. Pump current generated by the α2 Na,K-ATPase, Ip, was identified as the outward current activated by K+ and inhibited by micromolar ouabain. Ip was outward at all potentials studied (−90 to −30 mV) and increased with depolarization in the subthreshold range, −90 to −50 mV. The Q10 was 2.1 over the range of 22–37°C. The K1/2,K of Ip was 4.3 ± 0.3 mM at −90 mV and was relatively voltage independent. This K+ affinity is lower than that reported for other cell types but closely matches the dynamic range of extracellular K+ concentrations in the T-tubules. During muscle contraction, T-tubule luminal K+ increases in proportion to the frequency and duration of action potential firing. This K1/2,K predicts a low fractional occupancy of K+ substrate sites at the resting extracellular K+ concentration, with occupancy increasing in proportion to the frequency of membrane excitation. The stimulation of preexisting pumps by greater K+ site occupancy thus provides a rapid mechanism for increasing α2 activity in working muscles.  相似文献   

13.
The influence of NO3 uptake and reduction on ionic balance in barley seedlings (Hordeum vulgare, cv. Compana) was studied. KNO3 and KCl treatment solutions were used for comparison of cation and anion uptake. The rate of Cl uptake was more rapid than the rate of NO3 uptake during the first 2 to 4 hours of treatment. There was an acceleration in rate of NO3 uptake after 4 hours resulting in a sustained rate of NO3 uptake which exceeded the rate of Cl uptake. The initial (2 to 4 hours) rate of K+ uptake appeared to be independent of the rate of anion uptake. After 4 hours the rate of K+ uptake was greater with the KNO3 treatment than with the KCl treatment, and the solution pH, cell sap pH, and organic acid levels with KNO3 increased, relative to those with the KCl treatment. When absorption experiments were conducted in darkness, K+ uptake from KNO3 did not exceed K+ uptake from KCl. We suggest that the greater uptake and accumulation of K+ in NO3-treated plants resulted from (a) a more rapid, sustained uptake and transport of NO3 providing a mobile counteranion for K+ transport, and (b) the synthesis of organic acids in response to NO3 reduction increasing the capacity for K+ accumulation by providing a source of nondiffusible organic anions.  相似文献   

14.
Pleurotus ferulae is a mushroom typically found in arid steppe that is distributed widely in the Junggar Basin of Xinjiang, China. In this work, laccase production by P. ferulae JM30X was optimized in terms of medium composition and culture conditions. After optimization, the highest laccase activity obtained was 6,832.86 U/L. A single isozyme with a molecular weight of 66 kDa was observed by SDS-PAGE and native-PAGE. Optimum pH and temperature were 3.0 and 50–70 °C, respectively. The best laccase substrate was ABTS, for which the Michaelis-Menten constant (K m) and catalytic efficiency (K cat/K m) value for P. ferulae laccase were 0.193 mM and 2.73?×?106 (mM s)?1, respectively. The activity of purified laccase was increased by more than four-fold by Cu2+, Mn2+ and Mg2+, while it was completely inhibited by Fe2+ and Fe3+. The production of laccase was influenced by the initial pH and K+ concentration, and the activity of purified laccase was enhanced by Cu2+, Mn2+ and Mg2+. This Pleurotus genus laccase from P. ferulae JM30X was analyzed by MS spectrum and the results are conducive to furthering our understanding of Pleurotus genus laccases.  相似文献   

15.
Susceptible corn roots exposed to the host-selective toxin of Helminthosporium carbonum took up and retained more NO3, Na+, Cl, 3-o-methylglucose, and leucine than did control roots. Stimulatory effects on uptake were more pronounced with freshly cut roots than with roots that were washed and aged. Solutes were accumulated against a concentration gradient, and toxin-treated tissues developed a steeper gradient than did control tissues. Toxin affected both the low and high affinity uptake systems for Na+ and Cl. Toxin did not affect uptake of Na2, K+, Ca2+, phosphate ion (H2PO4 and HPO4), SO4, and glutamic acid. No toxin-induced leakage of any solute tested was detected within 5 to 6 hr after initial exposure to toxin. The data suggest that toxin from H. carbonum does not cause the general plasma membrane derangement caused by other host-selective toxins. Instead, H. carbonum toxin may cause specific changes in characteristics of the plasmalemma, which result in increased uptake of certain solutes.  相似文献   

16.
Protoplasts were enzymically isolated from suspension cultured cells of Nicotiana glutinosa L. and aspects of transport selectivity and kinetics were studied. In the presence of Ca2+, transport was selective for K+ (86Rb) over Na+. 36Cl transport was inhibited by Br or I but not by H2PO4. The kinetic data for short term (30 minutes) K+ influx over the range of 0.05 to 100 millimolar KCl were complex but similar to those observed in other plant tissues. In contrast, the kinetic data for Cl and H232PO4 over the same concentration range were different from those observed for K+, and could be accounted for by a single isotherm in the range of 0.05 to 4 millimolar and by an almost linear increase in influx rate above 4 millimolar. The kinetic data for Cl transport into intact cultured cells were identical in character to those observed for isolated protoplasts. The results support the view that enzymic removal of the cell wall produced no significant alteration in the transport properties of the protoplast.  相似文献   

17.
Four selected NaCl-tolerant cell lines of Sour orange (Citrus aurantium) were compared with the nonselected cell line in their growth and internal ion content of Na+, K+, and Cl when exposed to increasing NaCl concentrations. No difference was found among the various NaCl-tolerant cell lines in Na+ and Cl uptake, and all these cell lines took up similar or even larger amounts of Na+ and Cl than the NaCl-sensitive cell line. Exposure of cells of NaCl-sensitive and NaCl-tolerant lines to equal external concentrations of NaCl, resulted in a greater loss of K+ from the NaCl-sensitive cell line. This observation leads to the conclusion that growth and ability to retain high levels of internal K+ are correlated. Exposure of the NaCl-tolerant cell lines to salts other than NaCl resulted in even greater tolerance to Na2SO4, but rather poor tolerance to K+ introduced as either K2SO4 or KCl; the latter has a stronger inhibitory effect. The NaCl-sensitive cell line proved to be more sensitive to replacement of Na+ by K+. Analyses of internal Na+, K+, and Cl concentrations failed to identify any particular internal ion concentration which could serve as a reliable marker for salt tolerance.  相似文献   

18.
Mg:ATP-dependent H+ pumping has been studied in microsomal vesicles from 24-hour-old radish (Raphanus sativus L.) seedlings by monitoring both intravesicular acidification and the building up of an inside positive membrane potential difference (Δ ψ). ΔpH was measured as the decrease of absorbance of Acridine orange and Δ ψ as the shift of absorbance of bis(3-propyl-5-oxoisoxazol-4-yl)pentamethine oxonol. Both Mg:ATP-dependent Δ pH and Δ ψ generation are completely inhibited by vanadate and insensitive to oligomycin; moreover, Δ pH generation is not inhibited by NO3. These findings indicate that this membrane preparation is virtually devoid of mitochondrial and tonoplast H+-ATPases. Both intravesicular acidification and Δ ψ generation are influenced by anions: Δ pH increases and Δ ψ decreases following the sequence SO42−, Cl, Br, NO3. ATP-dependent H+ pumping strictly requires Mg2+. It is very specific for ATP (apparent Km 0.76 millimolar) compared to GTP, UTP, CTP, ITP. Δ pH generation is inhibited by CuSO4 and diethylstilbestrol as well as vanadate. Δ pH generation is specificially stimulated by K+ (+ 80%) and to a lesser extent by Na+ and choline (+28% and +14%, respectively). The characteristics of H+ pumping in these microsomal vesicles closely resemble those described for the plasma membrane ATPase partially purified from several plant materials.  相似文献   

19.
Six-year (2005–2010) evolution of water chemistry (Cl, NO3 , SO4 2−, HCO3 , Na+, K+, Ca2+ and Mg2+) and their interactions with morphological properties (i.e., slope and area), land cover, and hydrological seasonality were examined to identify controlling factors and processes governing patterns of stream water quality in the upper Han River, China. Correlation analysis and stepwise multiple regression models revealed significant correlations between ions (i.e., Cl, SO4 2−, Na+ and K+) and land cover (i.e., vegetation and bare land) over the entire catchment in both high- and low-flow periods, and in the buffer zone the correlation was much more stronger in the low-flow period. Catchment with steeper slope (>15°) was negatively correlated with major ions, largely due to multicollinearity of basin characteristics. Land cover within the buffer zone explained slightly less of major elements than at catchment scale in the rainy season, whereas in the dry season, land cover along the river networks in particular this within 100 m riparian zone much better explained major elements rather than this over the entire catchment. Anthropogenic land uses (i.e., urban and agriculture) however could not explain water chemical variables, albeit EC, TDS, anthropogenic markers (Cl, NO3 , SO4 2), Na+, K+ and Ca2+ significantly increased during 2005–2010, which was corroborated by principal component analyses (PCA) that indicated anthropogenic inputs. Observations demonstrated much higher solute concentrations in the industrial-polluted river. Our results suggested that seasonal evolution of water quality in combined with spatial analysis at multiple scales should be a vital part of identifying the controls on spatio-temporal patterns of water quality.  相似文献   

20.
We examined nitrate-dependent Fe2+ oxidation mediated by anaerobic ammonium oxidation (anammox) bacteria. Enrichment cultures of “Candidatus Brocadia sinica” anaerobically oxidized Fe2+ and reduced NO3 to nitrogen gas at rates of 3.7 ± 0.2 and 1.3 ± 0.1 (mean ± standard deviation [SD]) nmol mg protein−1 min−1, respectively (37°C and pH 7.3). This nitrate reduction rate is an order of magnitude lower than the anammox activity of “Ca. Brocadia sinica” (10 to 75 nmol NH4+ mg protein−1 min−1). A 15N tracer experiment demonstrated that coupling of nitrate-dependent Fe2+ oxidation and the anammox reaction was responsible for producing nitrogen gas from NO3 by “Ca. Brocadia sinica.” The activities of nitrate-dependent Fe2+ oxidation were dependent on temperature and pH, and the highest activities were seen at temperatures of 30 to 45°C and pHs ranging from 5.9 to 9.8. The mean half-saturation constant for NO3 ± SD of “Ca. Brocadia sinica” was determined to be 51 ± 21 μM. Nitrate-dependent Fe2+ oxidation was further demonstrated by another anammox bacterium, “Candidatus Scalindua sp.,” whose rates of Fe2+ oxidation and NO3 reduction were 4.7 ± 0.59 and 1.45 ± 0.05 nmol mg protein−1 min−1, respectively (20°C and pH 7.3). Co-occurrence of nitrate-dependent Fe2+ oxidation and the anammox reaction decreased the molar ratios of consumed NO2 to consumed NH4+ (ΔNO2/ΔNH4+) and produced NO3 to consumed NH4+ (ΔNO3/ΔNH4+). These reactions are preferable to the application of anammox processes for wastewater treatment.  相似文献   

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