The effects of NH4+ and NO3− on growth,resource allocation and nitrogen uptake kinetics of Phragmites australis and Glyceria maxima

The effects of NH₄⁺ or NO₃⁻ on growth, resource allocation and nitrogen (N) uptake kinetics of two common helophytes Phragmites australis (Cav.) Trin. ex Steudel and Glyceria maxima (Hartm.) Holmb. were studied in semi steady-state hydroponic cultures. At a steady-state nitrogen availability of 34 μM the growth rate of Phragmites was not affected by the N form (mean RGR = 35.4 mg g⁻¹ d⁻¹), whereas the growth rate of Glyceria was 16% higher in NH₄⁺-N cultures than in NO₃⁻-N cultures (mean = 66.7 and 57.4 mg g⁻¹ d⁻¹ of NH₄⁺ and NO₃⁻ treated plants, respectively). Phragmites and Glyceria had higher S/R ratio in NH₄⁺ cultures than in NO₃⁻ cultures, 123.5 and 129.7%, respectively.Species differed in the nitrogen utilisation. In Glyceria, the relative tissue N content was higher than in Phragmites and was increased in NH₄⁺ treated plants by 16%. The tissue NH₄⁺ concentration (mean = 1.6 μmol g fresh wt⁻¹) was not affected by N treatment, whereas NO₃⁻ contents were higher in NO₃⁻ (mean = 1.5 μmol g fresh wt⁻¹) than in NH₄⁺ (mean = 0.4 μmol g fresh wt⁻¹) treated plants. In Phragmites, NH₄⁺ (mean = 1.6 μmol g fresh wt⁻¹) and NO₃⁻ (mean = 0.2 μmol g fresh wt⁻¹) contents were not affected by the N regime. Species did not differ in NH₄⁺ (mean = 56.5 μmol g⁻¹ root dry wt h⁻¹) and NO₃⁻ (mean = 34.5 μmol g⁻¹ root dry wt h⁻¹) maximum uptake rates (V_max), and V_max for NH₄⁺ uptake was not affected by N treatment. The uptake rate of NO₃⁻ was low in NH₄⁺ treated plants, and an induction phase for NO₃⁻ was observed in NH₄⁺ treated Phragmites but not in Glyceria. Phragmites had low K_m (mean = 4.5 μM) and high affinity (10.3 l g⁻¹ root dry wt h⁻¹) for both ions compared to Glyceria (K_m = 6.3 μM, affinity = 8.0 l g⁻¹ root dry wt h⁻¹). The results showed different plasticity of Phragmites and Glyceria toward N source. The positive response to NH₄⁺-N source may participates in the observed success of Glyceria at NH₄⁺ rich sites, although other factors have to be considered. Higher plasticity of Phragmites toward low nutrient availability may favour this species at oligotrophic sites.     

Carbon and nitrogen metabolism of an eutrophication tolerative macrophyte,Potamogeton crispus,under NH4+ stress and low light availability

Submersed macrophytes in eutrophic lakes often experience high NH₄⁺ concentration and low light availability in the water column. This study found that an NH₄⁺–N concentration of 1 mg L^?1 in the water column apparently caused physiological stress on the macrophyte Potamogeton crispus L. The plants accumulated free amino acids (FAA) and lost soluble carbohydrates (SC) under NH₄⁺ stress. These stressful effects of NH₄⁺ were exacerbated under low light availability. Shading significantly increased NH₄⁺ and FAA contents and dramatically decreased SC and starch contents in the plant shoots. At an NH₄⁺–N concentration of 1 mg L^?1 in the water column, neither growth inhibition nor NH₄⁺ accumulation was observed in the plant tissues of P. crispus under normal light availability. The results showed that 1 mg L^?1 NH₄⁺–N in the water column was not toxic to P. crispus in a short term. To avoid NH₄⁺ toxicity, active NH₄⁺ transportation out of the cell may cost energy and thus result in a decline of carbohydrate. When NH₄⁺ inescapably accumulates in the plant cell, i.e. under NH₄⁺ stress and shading, NH₄⁺ is scavenged by FAA synthesis.     

Impact of NH4+ nitrogen source on the production of Rhizopus oryzae lipase in Pichia pastoris

BackgroundPichia pastoris is a highly successful system for heterologous expression. During the induction stage, the ammonium ion released into the fermentation broth has a deep impact on cell growth and protein expression. The impact of NH₄⁺ concentration on the expression of the Rhizopus oryzae lipase proAROL in P. pastoris was investigated.ResultsThe lipase activity under the optimum NH₄⁺ concentration of 440 mmol/L reached 12,019 U/mL. Increased concentrations of NH₄⁺ in the broth prevented the protease production, resulting in higher specific lipase activity in the supernatant. Furthermore, analysis of carbon metabolism and energy regeneration pattern revealed that under the definite NH₄⁺ concentrations more carbon source (methanol) was consumed with surged AOX activity and then the higher energy and amino acid precursors demand for recombinant protein synthesis is compensated for by the TCA cycle.ConclusionsIn this study, the R. oryzae lipase activity reaches the highest level ever reported under optimized NH₄⁺ concentration and the analysis of the carbon metabolism provides useful information for future optimization of protein production by P. pastoris in a molecular level.     

The effects of calcium sulphate on growth,membrane stability and nutrient uptake of tomato plants grown under salt stress

A pot experiment was carried out with tomato (Lycopersicon esculentum Mill.) cv. “Target F1” in a mixture of peat, perlite, and sand (1:1:1) to investigate the effects of supplementary calcium sulphate on plants grown at high NaCl concentration (75 mM). The treatments were: (i) control (C), nutrient solution alone; (ii) salt treatment (C + S), 75 mM NaCl; (iii) salt plus calcium treatment 1 (C + S + Ca1), 75 mM NaCl plus additional mixture of 2.5 mM CaSO₄ in nutrient solution; (iv) salt plus calcium treatment 2 (C + S + Ca2), 75 mM NaCl plus additional mixture of 5 mM CaSO₄ in nutrient solution. The plants grown under salt stress produced low dry matter, fruit weight, and relative water content than those grown in standard nutrient solution. Supplemental calcium sulphate added to nutrient solution containing salt significantly improved growth and physiological variables affected by salt stress (e.g. plant growth, fruit yield, and membrane permeability) and also increased leaf K⁺, Ca²⁺, and N in tomato plants. The effects of supplemental CaSO₄ in maintaining membrane permeability, increasing concentrations of Ca²⁺, N, and K⁺ and reducing concentration of Na⁺ (because of cation competition in root zone) in leaves could offer an economical and simple solution to tomato crop production problems caused by high salinity.     

Uptake of dissolved inorganic and organic nitrogen by the benthic toxic dinoflagellate Ostreopsis cf. ovata

Environmental factors that shape dynamics of benthic toxic blooms are largely unknown. In particular, for the toxic dinoflagellate Ostreopsis cf. ovata, the importance of the availability of nutrients and the contribution of the inorganic and organic pools to growth need to be quantified in marine coastal environments. The present study aimed at characterizing N-uptake of dissolved inorganic and organic sources by O. cf. ovata cells, using the ¹⁵N-labelling technique. Experiments were conducted taking into account potential interactions between nutrient uptake systems as well as variations with the diel cycle. Uptake abilities of O. cf. ovata were parameterized for ammonium (NH₄⁺), nitrate (NO₃⁻) and N-urea, from the estimation of kinetic and inhibition parameters. In the range of 0 to 10 μmol N L⁻¹, kinetic curves showed a clear preference pattern following the ranking NH₄⁺ > NO₃⁻ > N-urea, where the preferential uptake of NH₄⁺ relative to NO₃⁻ was accentuated by an inhibitory effect of NH₄⁺ concentration on NO₃⁻ uptake capabilities. Conversely, under high nutrient concentrations, the preference for NH₄⁺ relative to NO₃⁻ was largely reduced, probably because of the existence of a low-affinity high capacity inducible NO₃⁻ uptake system. Ability to take up nutrients in darkness could not be defined as a competitive advantage for O. cf. ovata. Species competitiveness can also be defined from nutrient uptake kinetic parameters. A strong affinity for NH₄⁺ was observed for O. cf. ovata cells that may partly explain the success of this toxic species during the summer season in the Bay of Villefranche-sur-mer (France).     

Effects of nutrients on arsenic accumulation by arsenic hyperaccumulator Pteris vittata L.

This research investigated the effects of various nutrients on arsenic (As) removal by arsenic hyperaccumulator Pteris vittata L. in a Hoagland nutrient solution (HNS). The treatments included different concentrations of Ca and K in 20% strength of HNS, different strengths of HNS (10, 20 and 30%), different strengths of HNS (10 and 20%) with and without CaCO₃, and different concentrations of Ca, K, NO₃, NH₄, and P in 20% strength of HNS. The plants were grown in nutrient solution containing 1 mg As L^?1 for 4 weeks except the Ca/K experiment where the plants were grown in nutrient solution containing 10 or 50 mg As L^?1 for 1 week. Adding up to 4 mM Ca or 3 mM K to 20% strength HNS significantly (P < 0.05) increased plant arsenic accumulation when the solution contained 10 mg As L^?1. Plant arsenic removal was reduced with increasing Ca and K concentrations at 50 mg As L^?1. Lower strength of HNS (10%) resulted in the greatest plant arsenic removal (79%) due to lower competition of P with As for plant uptake. Addition of CaCO₃ to 20% strength of HNS significantly increased arsenic removal by P. vittata. Among the nutrients tested, NO₃ and CaCO₃ were beneficial to plant arsenic removal while NH₄, P and Cl had adverse effects. This experiment demonstrated that it is possible to optimize plant arsenic removal by adjusting nutrients in the growth medium.     

Uptake and inhibition kinetics of nitrogen in Microcystis aeruginosa: Results from cultures and field assemblages collected in the San Francisco Bay Delta,CA

The nitrogen (N) uptake kinetic parameters for Microcystis field assemblages collected from the San Francisco Bay Delta (Delta) in 2012 and non-toxic and toxic laboratory culture strains of M. aeruginosa were assessed. The ¹⁵N tracer technique was used to investigate uptake of ammonium (NH₄⁺), nitrate (NO₃⁻), urea and glutamic acid over short-term incubations (0.5–1 h), and to study inhibition of NO₃⁻, NH₄⁺ and urea uptake by NH₄⁺, NO₃⁻ and NH₄⁺, respectively. This study demonstrates that Delta Microcystis can utilize different forms of inorganic and organic N, with the greatest capacity for NH₄⁺ uptake and the least for glutamic acid uptake, although N uptake did not always follow the classic Michaelis–Menten hyperbolic relationship at substrate concentrations up to 67 μmol N L⁻¹. Current ambient N concentrations in the Delta may be at sub-saturating levels for N uptake, indicating that if N loading (especially NH₄⁺) were to increase, Delta Microcystis assemblages have the potential for increased N uptake rates. Delta Microcystis had the highest specific affinity, α, for NH₄⁺ and the lowest for NO₃⁻. In culture, N uptake by non-toxic and toxic M. aeruginosa strains was much higher than from the field, but followed similar N utilization trends to those in the field. Neither strain showed severe inhibition of NO₃⁻ uptake by NH₄⁺ or inhibition of NH₄⁺ uptake on NO₃⁻, but both strains showed some inhibition of urea uptake by NH₄⁺.     

Salt tolerance in the halophyte Salicornia dolichostachya Moss: Growth,morphology and physiology

Salinization of agricultural land is an increasing problem. Because of their high tolerance to salinity, Salicornia spp. could become models to study salt tolerance; they also represent promising saline crops. The salinity-growth response curve for Salicornia dolichostachya Moss was evaluated at 12 salt concentrations in a hydroponic study in a greenhouse and at 5 different seawater dilutions in an outside setting. Salt concentrations ranged between 0 mM and 500 mM NaCl (≈seawater salinity). Plants were grown for six weeks and morphological and physiological adaptations in different tissues were evaluated.S. dolichostachya had its growth optimum at 300 mM NaCl in the root medium, independent of the basis on which growth was expressed. The relative growth rate (RGR) in the greenhouse experiment was comparable with RGR-values in the outdoor growth experiment. Leaf succulence and stem diameter had the highest values at the growth optimum (300 mM NaCl). Carbon isotope discrimination (δ¹³C) decreased upon salinity. S. dolichostachya maintained a lower leaf sap osmotic potential relative to the external solution over the entire salinity range, this was mainly accomplished by accumulation of Na⁺ and Cl⁻. Glycine betaine concentrations did not significantly differ between the treatments. Na⁺:K⁺-ratio and K⁺-selectivity in the shoots increased with increasing salinity, both showed variation between expanding and expanded shoot tissue. We conclude that S. dolichostachya was highly salt tolerant and showed salt requirement for optimal growth. Future growth experiments should be done under standardized conditions and more work at the tissue and cellular level needs to be done to identify the underlying mechanisms of salt tolerance.     

Differential tolerance to combined salinity and O2 deficiency in the halophytic grasses Puccinellia ciliata and Thinopyrum ponticum: The importance of K+ retention in roots

Saline environments of terrestrial halophytes are often prone to waterlogging, yet the effects on halophytes of combined salinity and waterlogging have rarely been studied. Either salinity or hypoxia (low O₂) alone can interfere with K⁺ homeostasis, therefore the combination of salinity or hypoxia is expected to impact significantly on K⁺ retention in roots. We studied mechanisms of tolerance to the interaction of salinity with hypoxia in Puccinellia ciliata and Thinopyrum ponticum, halophytic grasses that differ in waterlogging tolerance. Plants were exposed to aerated and stagnant saline (250 mM NaCl) treatments with low (0.25 mM) and high (4 mM) K⁺ levels; growth, net ion fluxes and tissue ion concentrations were determined. P. ciliata was more tolerant than T. ponticum to stagnant-saline treatment, producing twice the biomass of adventitious roots, which accumulated high levels of Na⁺, and had lower shoot Na⁺. After 24 h of saline hypoxic treatment, MIFE measurements revealed a net uptake of K⁺ (∼40 nmol m⁻² s⁻¹) for P. ciliata, but a net loss of K⁺ (∼20 nmol m⁻² s⁻¹) for the more waterlogging sensitive T. ponticum. NaCl alone induced K⁺ efflux from roots of both species, with channel blocker tests implicating GORK-like channels. P. ciliata had constitutively a more negative root cell membrane potential than T. ponticum (−150 versus −115 mV). Tolerance to salinity and hypoxia in P. ciliata is related to increased production of adventitious roots, regulation of shoot K⁺/Na⁺, and a superior ability to maintain negative membrane potential in root cells, resulting in greater retention of K⁺.     

Influence of ionic interactions on essential oil and phenolic diterpene composition of Dalmatian sage (Salvia officinalis L.)

The potential of four essential cations (K⁺, Ca²⁺, Mg²⁺ and Fe²⁺) to alleviate salt toxicity was studied in sage (Salvia officinalis L.) plants grown in pots. Two concentrations of the following chloride salts: KCl, CaCl₂, MgCl₂ and FeCl_3, were used together with 100 mM NaCl to study the effects of these nutrients on plant growth, leaf essential oils (EOs) and phenolic diterpenes composition. The sage plants accumulated Na⁺ in their leaves (includers); this has affected secondary metabolites’ biosynthesis. Treatment with 100 mM NaCl slightly decreased borneol and viridiflorol, while increased manool concentrations. Addition of KCl, CaCl₂ and MgCl₂ increased considerably in a dose-dependent manner the oxygen-containing monoterpenes (1.8-cineole, camphor, β-thujone and borneol) in 100 mM NaCl-treated sage. Whereas, the contents of viridiflorol decreased further with the addition of KCl in 100 mM NaCl-treated sage. Our results suggest that the changes in EOs composition were more related to K⁺ and Ca²⁺ availability than to Na⁺ toxicity. Furthermore, treatment with NaCl decreased by 50% carnosic acid (CA), a potent antioxidant, content in the leaves. K⁺ and Ca²⁺ promoted the accumulation of CA and its methoxylated form (MCA) in the leaves. The concentration of CA was positively correlated with leaf K⁺ (r = 0.56, P = 0.01) and Ca²⁺ (r = 0.44, P = 0.05) contents. It appears that different salt applications in combination with NaCl treatments had a profound effect on EOs and phenolic diterpene composition in sage. Therefore, ionic interactions may be carefully considered in the cultivation of this species to get the desired concentrations of these secondary metabolites in leaf extracts.     

Effect of two nutrient solution temperatures on nitrate uptake,nitrate reductase activity,NH4+ concentration and chlorophyll a fluorescence in rose plants

The effect of two nutrient solution temperatures (cold (10 °C) and warm (22 °C)) during two flowering events of rose plants (Rosa × hybrida cv. Grand Gala) were examined by measuring chlorophyll (Chl) a fluorescence, ammonium (NH₄⁺) content and nitrate reductase (NR) activity in four different leaf types, that is, external and internal leaves of bent shoots and lower and upper leaves of flowering stems. Besides, nitrate (NO₃^?) uptake and water absorption, total nitrogen (N) concentration in the plant, dry biomass, and the ratios of shoot/root and thin-white roots/suberized-brown roots were determined. Generally, cold solution increased NO₃^? uptake and thin-white roots production but decreased water uptake, so plants grown at cold solution had to improve their NO₃^? uptake mechanisms to obtain a higher amount of nutrient with less water absorption than plants grown at warm solution. The higher NO₃^? uptake can be related to an increase in NR activity, NH₄⁺ content and total N concentration at cold solution. Nutrient solution temperature also had an effect on the photosynthetic apparatus. In general terms, the effective quantum yield (?_PSII) and the fraction of open PSII reaction centres (q_L) were higher in rose plants grown at cold solution. These effects can be associated to a higher NO₃^? uptake and total N concentration in the plants and were modulated by irradiance throughout all the experiment. Plants could adapt to cold solution by enhancing their metabolism without a decrease in total dry biomass. Nevertheless, the effect of nutrient solution temperature is not simple and also affected by climatic factors.     

Effect of NH+4 and K+ on the activity of the ribosomal subunits in the EF-G- and EF-T-dependent GTR hydrolysis

$\text{E. coli}$ 50S ribosomal subunits show in the absence of 30S subunits and at low NH₄⁺ or K⁺ high turnover activity in EF-G-dependent GTP hydrolysis which is inhibited by increasing concentrations of monovalent cations. At 80 mM NH₄⁺ or K⁺ this activity is already 70–80% inhibited. This effect is reversed by 30S which are stimulatory with an optimum at about 80 mM for NH₄⁺ and 20–40 mM for K⁺. At low NH₄⁺ or K⁺ (<5 mM) stimulation by 30S of maximal 50S activity depends on the [EF-G]/[50S]. Unlike EF-G, EF-T does not show any Phe-tRNA-dependent GTPase activity with 50S alone even at low concentrations of NH₄⁺ or K⁺.     

Amperometric xanthine biosensors based on electrodeposition of platinum on polyvinylferrocenium coated Pt electrode

Novel xanthine biosensors were successfully fabricated by immobilizing xanthine oxidase on polyvinylferrocenium perchlorate matrix (PVF⁺ClO₄⁻) and platinum electrodeposited polyvinylferrocenium perchlorate matrix. PVF⁺ClO₄⁻ film was coated on Pt electrode at +0.7 V vs. Ag/AgCl by electrooxidation of polyvinylferrocene (PVF). Platinum nanoparticles were deposited on PVF⁺ClO₄⁻ electrode by electrochemical deposition in 2.0 mM H₂PtCl₆ solution at −0.2 V. Xanthine oxidase was incorporated into the polymer matrix via ion exchange process by immersing modified Pt electrodes in the enzyme solution. The amperometric responses of the biosensors were measured via monitoring oxidation current of hydrogen peroxide at +0.5 V. Under the optimal conditions, the linear ranges of xanthine detection were determined as 1.73 × 10⁻³–1.74 mM for PVF⁺XO⁻ and 0.43 × 10⁻³–2.84 mM for PVF⁺XO⁻/Pt. The detection limits of xanthine were 5.20 × 10⁻⁴ mM for PVF⁺XO⁻ and 1.30 × 10⁻⁴ mM for PVF⁺XO⁻/Pt. Moreover, the effects of applied potential, electrodeposition potential, H₂PtCl₆ concentration, amount of electrodeposited Pt nanoparticles, thickness of polymeric film, temperature, immobilization time, xanthine and xanthine oxidase concentrations on the response currents of the biosensors were investigated in detail. The effects of interferents, the operational and storage stabilities of biosensors and the applicabilities to drug samples of the biosensors analysis were also evaluated.     

Diurnal exchanges of CO2 and CH4 across the water–atmosphere interface in a water chestnut meadow (Trapa natans L.)

CH₄ and CO₂ fluxes across the water–atmosphere interface were measured over a 24 h day–night cycle in a shallow oxbow lake colonized by the water chestnut (Trapa natans L.) (Lanca di Po, Northern Italy). Only exchanges mediated by macrophytes were measured, whilst gas ebullition was not considered in this study. Measurements were performed from 29 to 30 July 2005 with short incubations, when T. natans stands covered the whole basin surface with a mean dry biomass of 504 ± 91 g m⁻². Overall, the oxbow lake resulted net heterotrophic with plant and microbial respiration largely exceeding carbon fixation by photosynthesis. The water chestnut stand was a net sink of CO₂ during the day-light period (−60.5 ± 8.5 mmol m⁻² d⁻¹) but it was a net source at night (207.6 ± 6.1 mmol m⁻² d⁻¹), when the greatest CO₂ efflux rate was measured across the water surface (28.2 ± 2.4 mmol m⁻² h⁻¹). The highest CH₄ effluxes (6.6 ± 1.8 mmol m⁻² h⁻¹) were determined in the T. natans stand during day-time, whilst CH₄ emissions across the plant-free water surface were greatest at night (6.8 ± 2.1 mmol m⁻² h⁻¹). Therefore, we assumed that the water chestnut enhanced methane delivery to the atmosphere. On a daily basis, the oxbow lake was a net source to the atmosphere of both CO₂ (147.1 ± 10.8 mmol m⁻² d⁻¹) and CH₄ (116.3 ± 8.0 mmol m⁻² d⁻¹).     

KMUP-1 ameliorates monocrotaline-induced pulmonary arterial hypertension through the modulation of Ca2+ sensitization and K+-channel

AimsThis study investigates the actions of KMUP-1 on RhoA/Rho-kinase (ROCK)-dependent Ca²⁺ sensitization and the K⁺-channel in chronic pulmonary arterial hypertension (PAH) rats.Main methodsSprague–Dawley rats were divided into control, monocrotaline (MCT), and MCT + KMUP-1 groups. PAH was induced by a single intraperitoneal injection (i.p.) of MCT (60 mg/kg). KMUP-1 (5 mg/kg, i.p.) was administered once daily for 21 days to prevent MCT-induced PAH. All rats were sacrificed on day 22.Key findingsMCT-induced increased right ventricular systolic pressure (RVSP) and right ventricular hypertrophy were prevented by KMUP-1. In myograph experiments, KCl (80 mM), phenylephrine (10 µM) and K⁺ channel inhibitors (TEA, 10 mM; paxilline, 10 µM; 4-AP, 5 mM) induced weak PA contractions in MCT-treated rats compared to controls, but the PA reactivity was restored in MCT + KMUP-1-treated rats. By contrast, in β-escin- or α-toxin-permeabilized PAs, CaCl₂-induced (1.25 mM, pCa 5.1) contractions were stronger in MCT-treated rats, and this action was suppressed in MCT + KMUP-1-treated rats. PA relaxation in response to the ROCK inhibitor Y27632 (0.1 μM) was much higher in MCT-treated rats than in control rats. In Western blot analysis, the expression of Ca²⁺-activated K⁺ (BK_Ca) and voltage-gated K⁺ channels (Kv2.1 and Kv1.5), and ROCK II proteins was elevated in MCT-treated rats and suppressed in MCT + KMUP-1-treated rats. We suggest that MCT-treated rats upregulate K⁺-channel proteins to adapt to chronic PAH.SignificanceKMUP-1 protects against PAH and restores PA vessel tone in MCT-treated rats, attributed to alteration of Ca²⁺ sensitivity and K⁺-channel function.     

Effect of different macrophytes in abating nitrogen from a synthetic wastewater

An experiment conducted in an unheated glasshouse from October 2006 to March 2008 studied the efficiency of different macrophytes in reducing NO₃-N and NH₄-N concentrations and loads in synthetic wastewaters. The experimental setup consisted of plastic tanks, filled with gravel and vegetated with Carex elata All., Juncus effusus L., Phragmites australis (Cav.) Trin., Typhoides arundinacea L. Moench (syn Phalaris arundinacea L.) var. picta and Typha latifolia L. There was also a control without vegetation. From January to July, a solution of 50–60 ppm of NH₄-N and NO₃-N was applied monthly; then the input concentration was doubled. The total load at the end of the experimental period was 70.4 g/m² of NO₃-N and 67.3 of NH₄-N. At the end of each month, water was discharged from the tanks and analysed to determine the two nitrogen forms. At the end of the experiment, 33 g/m² of total N (almost 24% of applied N) had disappeared in the control. Among species, the highest abatement was detected in T. latifolia (72 g/m², almost 52% of applied N) and the lowest in J. effusus (35%).A weekly chemical analysis in July showed that a large amount of NH₄-N quickly disappeared in all treatments, while NO₃-N only decreased in the vegetated tanks. In December, NH₄-N had similar dynamics, while NO₃-N increased.All water volumes entering and exiting the tanks were measured in order to evaluate evapotranspiration. T. latifolia showed the highest water consumption, reaching a cumulative value of above 1000 mm.At the end of the experiment, J. effusus presented the highest amount of nitrogen stored in the aerial parts (5.63 g/m²) and T. latifolia the lowest (1.92 g/m²).     

Investigating CH4 and N2O emissions from eco-engineering wastewater treatment processes using constructed wetland microcosms

Methane (CH₄) and nitrous oxide (N₂O) are important greenhouse gases, because of their contribution to the global greenhouse effect. The present study assessed emissions of N₂O and CH₄ from constructed wetland microcosms, planted with Phragmites australis and Zizania latifolia, when treating wastewater under different biological oxygen demand (BOD) concentration conditions. The removal rate was 95% for BOD and more than 80% for COD in all three pollutant concentrations, both plants’ removal rates of pollutants were at almost the same level, and both were found to resist BOD concentrations as high as 200 mg L⁻¹. When BOD concentrations fell below 200 mg L⁻¹, the soil plant units reached an average of 80–92% T-N and T-P removal rates; however, as the concentrations increased to 200 mg mg L⁻¹ or when during the initial phases of winter, the removal rates for T-N and T-P decreased to less than 70%. With NH₃-N removal, the influences of BOD concentrations and air temperature were more obvious. When BOD concentrations increased to 100 mg L⁻¹ after October, an obvious decrease in NH₃-N removal was detected; almost no nitrification occurred beginning in December at BOD concentrations of 200 mg mg L⁻¹. N₂O and CH₄ emissions showed obvious seasonal changes; higher emissions were observed with higher BOD concentrations, especially among Z. latifolia units. The enumeration of methane-oxidizing bacteria and methane-producing bacteria was also conducted to investigate their roles in impacting methane emissions and their relationships with plant species. The pollutant purification potentials of P. australis and Z. latifolia plant units during wastewater treatment of different pollutant concentrations occurred at almost the same levels. The nutrient outflow and methane flux were consistently higher with Z. latifolia units and higher concentrations of BOD. The more reductive status and higher biomass of methanogens may be the reason for the lower nitrification and higher CH₄ emissions observed with Z. latifolia units and higher concentration systems. The Z. latifolia root system is shallow, and the activity of methanotrophs is primarily confined to the upper portion of the soil. However, the root system of P. australis is deeper and can oxidize methane to a greater depth. This latter structure is more favorable as it is better for reducing methane emissions from P. australis soil plant systems.     

Target Binding to S100B Reduces Dynamic Properties and Increases Ca2 +-Binding Affinity for Wild Type and EF-Hand Mutant Proteins

Mutations in the second EF-hand (D61N, D63N, D65N, and E72A) of S100B were used to study its Ca^2 + binding and dynamic properties in the absence and presence of a bound target, TRTK-12. With ^D63NS100B as an exception (^D63NK_D = 50 ± 9 μM), Ca^2 + binding to EF2-hand mutants were reduced by more than 8-fold in the absence of TRTK-12 (^D61NK_D = 412 ± 67 μM, ^D65NK_D = 968 ± 171 μM, and ^E72AK_D = 471 ± 133 μM), when compared to wild-type protein (^WTK_D = 56 ± 9 μM). For the TRTK-12 complexes, the Ca^2 +-binding affinity to wild type (^WT + TRTKK_D = 12 ± 10 μM) and the EF2 mutants was increased by 5- to 14-fold versus in the absence of target (^{D61N + TRTK}K_D = 29 ± 1.2 μM, ^{D63N + TRTK}K_D = 10 ± 2.2 μM, ^{D65N + TRTK}K_D = 73 ± 4.4 μM, and ^{E72A + TRTK}K_D = 18 ± 3.7 μM). In addition, R_ex, as measured using relaxation dispersion for side‐chain ¹⁵N resonances of Asn63 (^D63NS100B), was reduced upon TRTK-12 binding when measured by NMR. Likewise, backbone motions on multiple timescales (picoseconds to milliseconds) throughout wild type, ^D61NS100B, ^D63NS100B, and ^D65NS100B were lowered upon binding TRTK-12. However, the X-ray structures of Ca^2 +-bound (2.0 Å) and TRTK-bound (1.2 Å) ^D63NS100B showed no change in Ca^2 + coordination; thus, these and analogous structural data for the wild-type protein could not be used to explain how target binding increased Ca^2 +-binding affinity in solution. Therefore, a model for how S100B–TRTK‐12 complex formation increases Ca^2 + binding is discussed, which considers changes in protein dynamics upon binding the target TRTK-12.     

Two ways to achieve an anammox influent from real reject water treatment at lab-scale: Partial SBR nitrification and SHARON process

A comparative study to produce the correct influent for Anammox process from anaerobic sludge reject water (700–800 mg NH₄⁺-N L⁻¹) was considered here. The influent for the Anammox process must be composed of NH₄⁺-N and NO₂⁻-N in a ratio 1:1 and therefore only a partial nitrification of ammonium to nitrite is required. The modifications of parameters (temperature, ammonium concentration, pH and solid retention time) allows to achieve this partial nitrification with a final effluent only composed by NH₄⁺-N and NO₂⁻-N at the right stoichiometric ratio. The equal ratio of HCO₃⁻/NH₄⁺ in reject water results in a natural pH decrease when approximately 50% of NH₄⁺ is oxidised. A Sequencing batch reactor (SBR) and a chemostat type of reactor (single-reactor high activity ammonia removal over nitrite (SHARON) process) were studied to obtain the required Anammox influent. At steady state conditions, both systems had a specific conversion rate around 40 mg NH₄⁺-N g⁻¹ volatile suspended solids (VSS) h⁻¹, but in terms of absolute nitrogen removal the SBR conversion was 1.1 kg N day⁻¹ m⁻³, whereas in the SHARON chemostat was 0.35 kg N day⁻¹ m⁻³ due to the different hydraulic retention time (HRT) used. Both systems are compared from operational (including starvation experiments) and kinetic point of view and their advantages/disadvantages are discussed.