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PubMed2004

The presence of ammonium facilitates nitrite reduction under PHB driven simultaneous nitrification and denitrification.

For economic and efficient nitrogen removal from wastewater treatment plants via simultaneous nitrification and denitrification the nitrification process should stop at the level of nitrite such that nitrite rather than nitrate becomes the substrate for denitrification. This study aims to contribute to the understanding of the conditions that are necessary to improve nitrite reduction over nitrite oxidation. Laboratory sequencing batch reactors (SBRs) were operated with synthetic wastewater containing acetate as COD and ammonium as the nitrogen source. Computer controlled operation of the reactors allowed reproducible simultaneous nitrification and denitrification (SND). The oxygen supply was kept precisely at a low level of 0.5 mgL(-1) and bacterial PHB was the only electron donor available for denitrification. During SND little nitrite or nitrate accumulated (< 20% total N), indicating that the reducing processes were almost as fast as the production of nitrite and nitrate from nitrification. Nitrite spiking tests were performed to investigate the fate of nitrite under different oxidation (0.1-1.5 mgL(-1) of dissolved oxygen) and reduction conditions. High levels of reducing power were provided by allowing the cells to build up to 2.5 mM of PHB. Nitrite added was preferentially oxidised to nitrate rather than reduced even when dissolved oxygen was low and reducing power (PHB) was excessively high. However, the presence of ammonium enabled significant reduction of nitrite under low oxygen conditions. This is consistent with previous observations in SBR where aerobic nitrite and nitrate reduction occurred only as long as ammonium was present. As soon as ammonium was depleted, the rate of denitrification decreased significantly. The significance of the observed strongly stimulating effect of ammonium on nitrite reduction under SND conditions is discussed and potential consequences for SBR operation are suggested.

Acetates↗
PubMed2005

Nitrobacter and Nitrospira genera as representatives of nitrite-oxidizing bacteria: detection, quantification and growth along the lower Seine River (France).

Pollution from agriculture and urban effluents influences the ecology and biochemical functioning of the Seine River. Nitrification dominates nitrogen transformations downstream of the effluents of the Paris wastewater treatment plant (WWTP) at Achères, treating, by activated sludge the wastewater of 6.5 million inhabitant equivalents from Paris and its suburbs, without nitrification and denitrification treatment. It discharges effluents containing large amounts of nitrogen, ammonium mostly (approximately 30 mg L(-1) N-NH(4+) L(-1)), on average 45 mg L(-1) of suspended particulate matter, high quantities of total organic carbon (approximately 30 mg C L(-1)) largely biodegradable (40%), and high concentration in total phosphorus ( approximately 3 mg Tot P L(-1)), as well as microorganisms. Ammonium, brought into the river system, is slowly nitrified in the lower Seine River and especially in the freshwater estuary. The nitrifying activities can be observed by measuring inorganic nitrogen compound concentrations and potential activities. To understand the contributions of the WWTP effluents, the upstream agricultural runoff water and the Seine tributaries, it is useful to investigate the bacterial community. Whereas ammonia oxidation has been widely studied, the second step, i.e. nitrite oxidation, is less well understood. We have previously analysed the ammonium-oxidizing bacterial (AOB) community in the Seine (Cébron, A., Berthe, T., Garnier, J., 2003. Nitrification and nitrifying bacteria in the lower Seine River and estuary (France). Appl. Environ. Microbiol. 69, 7091-7100; Cébron, A., Coci, M., Garnier, J., Laanbroek, H.J., 2004. DGGE analysis of the ammonia oxidizing bacterial community structure in the lower Seine River: impact of the Paris wastewater effluents. Appl. Environ. Microbiol. 70, 6726-6737), and focus here on the composition of the nitrite-oxidizing bacterial (NOB) community. As no general molecular probe targeting all known NOBs is currently available, we chose to target and quantify (by competitive PCR) the two genera Nitrobacter and Nitrospira assumed to be the major players in nitrite oxidation in freshwater environments. Nitrobacter species were dominant in the upstream Seine River basin but Nitrospira was the dominant NOB downstream of the WWTP. These two genera were equally represented in WWTP effluents. In the Seine River estuary, especially in the salinity gradient, the Nitrobacter proportion increases and that of Nitrospira disappears, possibly due dilution by seawater.

Bacteria↗
PubMed1977

Electrocardiographic observation on goats with urea-ammonia poisoning and a consideration on the main cause of death.

Changes in electrocardiograms, blood pressure, pH, and partial pressure of gases (Po2 and Pco2) in arterial blood were studied in goats poisoned by urea or ammonium compounds under spontaneous and artificial respiration and in nonconvulsive state. Abnormal electrocardiogram patterns, such as ventricular flutter, ventricular premature beat, atrioventricular dissociation, depression of ST-segment and sinus tachycardia, were all observed after the occurrence of tetanic convulsion. The electrocardiogram pattern seen at the respiratory arrest showed sinus or supraventricular tachycardia; respiratory arrest preceded cardiac arrest in all the goats, but one. Blood pressure was markedly elevated, accompanied with tetanic convulsion. Po2 decreased gradually and the level was below 30 mm Hg (37.0 degrees C) at respiratory arrest and the final opisthotonus. Artificial respiration starting at the final opisthotonus could delay the cardiac arrest. Under nonconvulsive urea-poisoning with gallamine triethiodide and with artificial respiration of air or a mixture of air and oxygen to elevate the Po2 level, changes of electrocardiogram, blood pressure, and Po2 were similar to those seen under convulsive urea-poisoning. The main cause of death was discussed and presumed to be respiratory and cardiovascular failure.

Ammonia↗
PubMed1996

Modulation of ligand binding to components of the GABAA receptor complex by ammonia: implications for the pathogenesis of hyperammonemic syndromes.

The effects of 5-2500 microM concentrations of neutral ammonium salts on the binding of ligands to components of the GABAA receptor complex were investigated. [3H]Flunitrazepam binding to the benzodiazepine receptor was enhanced by ammonium (10-500 microM), but not sodium tartrate with EC50 = 98 microM and Emax = 31%. Further increasing ammonium tartrate concentrations (500-2500 microM) decreased [3H]flunitrazepam binding to control levels. The ammonium tartrate-induced increase in [3H]flunitrazepam binding was manifested as a 50% decrease in Kd. Furthermore, GABA increased the potency of ammonium tartrate in enhancing [3H]flunitrazepam binding by 63%. [3H]Ro 15-1788 and [3H]Ro 15-4513 binding to the benzodiazepine receptor was not significantly enhanced by ammonium tartrate (Emax approximately 13%). Ammonium tartrate also increased, then decreased the binding of 500 nM [3H]muscimol to the GABAA receptor (EC50 = 52 microM, Emax = 30%) in a concentration-dependent manner, but had no effect on [3H]SR 95-531 binding (Emax < 16%). The ammonium tartrate-induced alterations in [3H]muscimol binding were demonstrated in saturation assays as the loss of the high affinity binding site and a 27% increase in the Bmax of the low affinity binding site. These results indicate that ammonia biphasically enhances, then returns ligand binding to both the GABA and benzodiazepine receptor components of the GABAA receptor complex to control levels in a barbiturate-like fashion. This suggests that ammonia may enhance GABAergic neurotransmission at concentrations commonly encountered in hepatic failure, an event preceding the suppression of inhibitory neuronal function observed at higher (> 1 mM) ammonia concentrations. This increase in GABAergic neurotransmission is consistent with the clinical picture of lethargy, ataxia and cognitive deficits associated with liver failure and congenital hyperammonemia.

Ammonia↗
PubMed1992

Regulation of the glutamine content of astrocytes by cAMP and hydrocortisone: effect of pH.

It was reported recently that the glutamine content of astrocytes incubated with glutamate and ammonium is steeply dependent on the pH of the solution. The present study shows that pretreatment of astrocytes with dibutyryl cAMP or with hydrocortisone, conditions that induce glutamine synthetase activity, increased glutamine content 2.4-fold and 5.3-fold, respectively. Nevertheless, a shift of pH from 7.4 to 7.8 increased glutamine content further by 2.7-fold and 3.0-fold, respectively. The net rates of uptake of glutamate and export of glutamine varied narrowly compared to these very large changes in glutamine content.

Animals↗
PubMed2005

Deposition monitoring networks: what monitoring is required to give reasonable estimates of ammonia/ammonium?

Deposition is one of the main loss terms for ammonia and ammonium from the atmosphere. It is also the input for ecosystems that can lead to drastic changes and effects. Deposition networks are needed to evaluate the need and the effect of policies to reduce nitrogen emissions, but also for studying deposition parameters and for developing deposition models. As with ambient concentrations of ammonia, deposition, especially dry deposition, varies strongly in space and in time. Furthermore, the bi-directional surface-atmosphere exchange of ammonia makes the combination of ambient concentration measurements with inferential models inadequate. Developing deposition monitoring networks with reasonable accuracy and representativeness is therefore not straightforward. In Europe several projects have addressed deposition monitoring. From these results it is concluded that a monitoring strategy should consist of a network with a limited amount of super sites combined with a larger number of sites where low cost methods are applied, together with models for generalisation.

Air Pollutants↗
PubMed2002

Quantitative aspects of inorganic nutrient fluxes in the Gazi Bay (Kenya): implications for coastal ecosystems.

Fluxes of dissolved inorganic nutrients: NH4+, NO2-, NO3-, PO4(3-) and Si(OH)4 from nearshore sediments of Gazi Bay were measured in situ within mangrove, seagrass and coral reef biotopes using benthic flux bell-jar chambers of cross-sectional area 0.066 m2 and volume 0.0132 m3. The objectives were: (1) to determine the influence of benthic fluxes, fluvial discharge and seasonal variations on the nutrient budget in the Bay waters; (2) to determine the effect of tidal and spatial variations on nutrient loads in the water column and (3) to establish the relative importance of the nutrient sources with regard to total community production of the Bay. The directly measured fluxes ranged from -270 to +148 micromol NH4+-N/m2/h; -60 to +63 micromol NO2(-)-N/m2/h; -79 to +41 micromol NO3(-)-N/m2/h; -79 to +75 micromol PO4(3-)-P/m2/h and +30 to +350 micromol Si(OH)4-Si/m2/h for and respectively. It was established that benthic fluxes are the major sources of dissolved inorganic NH4+, NO2- and Si(OH)4 while fluvial sources are important for NO3- and PO4(3-) into Gazi Bay waters. Seasonal variations had an appreciable effect on the PO4(3-) fluxes, N:Si ratio, river nutrient discharge, plankton productivity and important environmental factors such as salinity and temperature. Tidal and spatial variations had no significant effect on nutrient concentrations and net fluxes within the water column. The results imply that benthic fluxes are largely responsible for the nutrient dynamics of the nearshore coastal ecosystems especially where direct terrestrial inputs do not contribute significantly to the nutrient budget.

Ammonia↗
PubMed2001

Bacillus subtilis glutamine synthetase controls gene expression through a protein-protein interaction with transcription factor TnrA.

Bacillus subtilis TnrA, a global regulator of transcription, responds to nitrogen availability, but the specific signal to which it responds has been elusive. Genetic studies indicate that glutamine synthetase is required for the regulation of TnrA activity in vivo. We report here that the feedback-inhibited form of glutamine synthetase directly interacts with TnrA and blocks the DNA binding activity of TnrA. Mutations in the tnrA gene (tnrA(C)) that allow constitutive high level expression of tnrA-activated genes were isolated and characterized. Feedback-inhibited glutamine synthetase had a significantly reduced ability to block the in vitro DNA binding by three of the TnrA(C) proteins. Thus, glutamine synthetase, an enzyme of central metabolism, directly interacts with and regulates the DNA binding activity of TnrA.

Amino Acid Sequence↗
PubMed1992

Might distal renal tubular acidosis be a proximal tubular cell disorder?

Incomplete renal tubular acidosis (RTA) and overt distal RTA may be different stages of the same underlying pathophysiology in certain individuals. The rationale that draws these conditions together is the relatively alkaline pH of the urine, hypocitraturia, and a possible familial association. The rate of excretion of ammonium (NH4+), on the other hand, suggests that these conditions stem from fundamentally different lesions. To explain this difference, we suggest that two possible disorders may result in the evolution from incomplete RTA to overt distal RTA. One subgroup could have gradient-limited distal RTA, while the other subgroup may have a lower pH of the intracellular fluid of the proximal convoluted tubular epithelium. Indices of proximal intracellular pH (rates of excretion of NH4+, NH3, and citrate) were culled from the literature spanning the years 1959 to 1991 on patients with incomplete RTA and overt distal RTA. Three points emerge: (1) the rate of excretion of NH4+ was lower in patients with overt distal RTA than in normals following an acute acid load (23 +/- 1 v 49 +/- 3 mumol/min); (2) the concentration of NH3 in the urine was almost 25-fold higher in incomplete RTA than in normals (69 +/- 14 v 3 +/- 0.4 nmol/min); and (3) in incomplete RTA, the pH of the urine fell to very low values (4.9 +/- 0.1) when high urine flows were induced with furosemide. The low pH of the urine would therefore suggest that many of these patients do not gradient-limited distal RTA, but more likely have proximal renal epithelial cell acidosis. We hypothesize that this high rate of excretion of NH4+ and low rate of excretion of citrate in the absence of acidosis or hypokalemia is consistent with proximal cell acidosis. To explain a transition from incomplete RTA to overt distal RTA, we speculate that toxicity of high concentrations of NH3 in the medullary interstitium as well as nephrolithiasis and nephrocalcinosis due to low urinary citrate and possibly an alkaline medullary interstitium may lead to damage of structures in this region.

Acid-Base Equilibrium↗
PubMed1999

A co-activator of nitrogen-regulated transcription in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, the transcription factors Gln3p and Nil1p of the GATA family play a determinant role in expression of genes that are subject to nitrogen catabolite repression. Here we report the isolation of a new yeast mutant, gan1-1, exhibiting dramatically decreased NAD-linked glutamate dehydrogenase (NAD-GDH) and glutamine synthetase (GS) activities. The GAN1 gene was cloned and found to encode a 488-amino-acid polypeptide bearing no typical DNA binding domain. Gan1p is required for full expression of GLN1, GDH2 and also other nitrogen utilization genes, including GAP1, PUT4, MEP2 and GDH1. The extent to which Gan1p is required, however, varies according to the gene and to the nitrogen source available. We show that Gan1p is in fact involved in Gln3p- and Nil1p-dependent transcription. In the case of Gln3p-dependent transcription, the degree to which Gan1p is required appears to be gene specific. The contribution of Gan1p to gene expression is also influenced by the nitrogen status of the cell. We found that GAN1 is identical to ADA1, which encodes a component of the ADA/GCN5 co-activator complex. Ada1/Gan1p thus represents the first reported case of an accessory protein (a co-activator) linking the GATA-binding proteins Gln3p and Nil1p, mediating nitrogen-regulated transcription, to the basal transcription machinery.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Light induces an increase in the pH of and a decrease in the ammonia concentration in the extrapallial fluid of the giant clam Tridacna squamosa.

The objective of this study was to examine whether 12 h of light exposure would lead to an increase in the pH of and a decrease in the concentration of total ammonia in the extrapallial fluid of the giant clam Tridacna squamosa. We also aimed to elucidate indirectly whether movements of ammonia and/or protons (H(+)) occurred between the extrapallial fluid and the outer mantle epithelium. The pH of the extrapallial fluid of T. squamosa exposed to 12 h of light was significantly higher than that of clams exposed to 12 h of darkness. Conversely, the total ammonia concentration in the extrapallial fluid of the former was significantly lower than that of the latter. In addition, the glutamine content in the mantle adjacent to the extrapallial fluid of clams exposed to 12 h of light was significantly greater than that of clams exposed to 12 h of darkness. These results suggest that in the extrapallial fluid of T. squamosa exposed to light, NH(3) combined with H(+) as NH(+)(4) and that NH(+)(4) was transported into the mantle and used as a substrate for glutamine formation. Injection of NH(4)Cl into the extrapallial fluid led to an instantaneous increase in the total ammonia concentration therein, but the total ammonia concentration decreased subsequently and returned to the control value within 1 h. This is in support of the proposition that NH(+)(4) could be transported from the extrapallial fluid to the mantle. Injection of HCl into the extrapallial fluid led to an instantaneous decrease in the pH of the extrapallial fluid. However, there was a significant increase in pH within 1 h in light or darkness, achieving a partial recovery toward the control pH value. The increase in pH within this 1-h period in light or darkness was accompanied by a significant decrease in the total ammonia concentration in the extrapallial fluid, which supports the proposition that H(+) could be transported in combination with NH(3) as NH(+)(4). Therefore, our results prompt a reexamination of the previous proposition that the removal of H(+) by NH(3) can facilitate calcification in molluscs in general and an investigation of the relationship between H(+) removal through NH(+)(4) transport and light-enhanced calcification in T. squamosa.

Ammonia↗
PubMed1978

Amino acid induced orotic aciduria.

Twenty amino acids were examined for their effects on urinary orotic acid excretion. Except for arginine and ornithine, all of the remaining amino acids tested induced a mild orotic aciduria in rats 2 hours post feeding. Two ammonium salts, and urease also acted, as inducers of orotic aciduria. The ammoneogenic properties of the amino acids tested could not solely explain the induced excretion of orotic acid. Only serine, glutamine, NH4Cl, (NH4)2CO3, and urease increased orotic acid excretion in the 24 hour fasted rat. Administration of 0.5 mmoles of arginine or ornithine ameliorated the mild orotic aciduria induced by either glycine or lysine. Arginine was shown to be more efficacious in preventing glycine induced orotic aciduria than was ornithine. Amino acid induced orotic aciduria is dependent upon the physiological state of the animal, varying with the state of digestion and the supply of arginine.

Amino Acids↗
PubMed1990

Fulminant hepatic failure in poisoning due to ingestion of T 61, a veterinary euthanasia drug.

A patient developed fulminant hepatic failure 48 h after the ingestion of T 61, a veterinary euthanasia drug which contains both general and local anesthetics, a neuromuscular blocking agent, and dimethylformamide (DMF) as a solvent. This is the first report of such severe hepatic manifestation in T 61 poisoning, the most common symptoms of which are early coma and respiratory failure due to the anesthetic and the neuromuscular blocking agent. In a very few cases mild and transitory symptoms of hepatic insufficiency have been observed. In this case the fulminant hepatic failure was due to the high dose (0.6 ml/kg) ingestion of DMF.

Amides↗
PubMed2001

Real time visualization of 13N-translocation in rice under different environmental conditions using positron emitting Ttacer imaging system.

The ammonium ion is an indispensable nitrogen source for crops, especially paddy rice (Oryza sativa L. cv Nipponbare). Until now, it has been impossible to measure ammonium uptake and nitrogen movement in plants in real time. Using the new technologies of PETIS (positron emitting tracer imaging system) and PMPS (positron multi-probe system), we were able to visualize the real time translocation of nitrogen and water in rice plants. We used positron-emitting 13N-labeled ammonium (13NH4+) and 15O-water to monitor the movement. In plants cultured under normal conditions, 13NH4+ supplied to roots was taken up, and a 13N signal was detected at the discrimination center, the basal part of the shoots, within 2 minutes. This rapid translocation of (13)N was almost completely inhibited by a glutamine synthetase inhibitor, methionine sulfoximine. In general, nitrogen deficiency enhanced 13N translocation to the discrimination center. In the dark, 13N translocation to the discrimination center was suppressed to 40% of control levels, whereas 15O-water flow from the root to the discrimination center stopped completely in the dark. In abscisic acid-treated rice, 13N translocation to the discrimination center was doubled, whereas translocation to leaves decreased to 40% of control levels. Pretreatment with NO3- for 36 hours increased 13N translocation from the roots to the discrimination center to 5 times of control levels. These results suggest that ammonium assimilation (from the roots to the discrimination center) depends passively on water flow, but actively on NH4+-transporter(s) or glutamine synthetase(s).

Biological Transport↗