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PubMed2006

Archaeal nitrification in the ocean.

Marine Crenarchaeota are the most abundant single group of prokaryotes in the ocean, but their physiology and role in marine biogeochemical cycles are unknown. Recently, a member of this clade was isolated from a sea aquarium and shown to be capable of nitrification, tentatively suggesting that Crenarchaeota may play a role in the oceanic nitrogen cycle. We enriched a crenarchaeote from North Sea water and showed that its abundance, and not that of bacteria, correlates with ammonium oxidation to nitrite. A time series study in the North Sea revealed that the abundance of the gene encoding for the archaeal ammonia monooxygenase alfa subunit (amoA) is correlated with a decline in ammonium concentrations and with the abundance of Crenarchaeota. Remarkably, the archaeal amoA abundance was 1-2 orders of magnitude higher than those of bacterial nitrifiers, which are commonly thought to mediate the oxidation of ammonium to nitrite in marine environments. Analysis of Atlantic waters of the upper 1,000 m, where most of the ammonium regeneration and oxidation takes place, showed that crenarchaeotal amoA copy numbers are also 1-3 orders of magnitude higher than those of bacterial amoA. Our data thus suggest a major role for Archaea in oceanic nitrification.

Archaeal Proteins↗
PubMed2006

Inhibitory complex of the transmembrane ammonia channel, AmtB, and the cytosolic regulatory protein, GlnK, at 1.96 A.

Ammonia conductance is highly regulated. A P(II) signal transduction protein, GlnK, is the final regulator of transmembrane ammonia conductance by the ammonia channel AmtB in Escherichia coli. The complex formed between AmtB and inhibitory GlnK at 1.96-A resolution shows that the trimeric channel is blocked directly by GlnK and how, in response to intracellular nitrogen status, the ability of GlnK to block the channel is regulated by uridylylation/deuridylylation at Y51. ATP and Mg(2+) augment the interaction of GlnK. The hydrolyzed product, adenosine 5'-diphosphate orients the surface of GlnK for AmtB blockade. 2-Oxoglutarate diminishes AmtB/GlnK association, and sites for 2-oxoglutarate are evaluated.

Adenosine Triphosphate↗
PubMed1994

Growth and regulation of enzyme synthesis in the nitrilotriacetic acid (NTA)-degrading bacterium Chelatobacter heintzii ATCC 29600.

In the aerobic bacterium Chelatobacter heintzii, growth and regulation of enzymes involved in nitrilotriacetic acid (NTA) degradation have been investigated in chemostat culture during cultivation with glucose, NTA or mixtures thereof. In batch culture mu max with NTA was 0.18 h-1 and with glucose 0.22 h-1. Growth yields for both substrates were reduced at low dilution rates. During growth with NTA specific activity of the NTA monooxygenase (NTA-MO) exhibited a maximum at D = 0.03 h-1 and gradually decreased with increasing dilution rates. In glucose-grown cells the specific activity as well as immunologically detectable NTA-MO protein was always close to the detection limit. During cultivation with different mixtures of NTA and glucose at a dilution rate of 0.06 h-1, both substrates were utilized simultaneously, irrespective of the NTA/glucose ratio and the presence of excess ammonia. Synthesis of both NTA-MO and iminodiacetic acid dehydrogenase became induced when NTA contributed to more than approximately 1-3% of the total carbon in the substrate mixture supplied. However, NTA was also degraded when the proportion of NTA in the mixture was lower than 1%, which is consistent with the low constitutive level of expression for NTA-MO observed. Results are discussed with respect to NTA biodegradation during sewage treatment and in ecosystems.

Bacterial Proteins↗
PubMed1995

Changes in amino acids, ammonium, and coagulation factors after transcervical resection of the endometrium with a glycine solution used for uterine irrigation.

OBJECTIVE: Transcervical resection of the endometrium with the use of 1.5% glycine for irrigation is associated with postoperative nausea in some patients. This could be because of hyponatremia or toxic effects of glycine and its metabolites. Moreover, 1.5% glycine is hypoosmolar, and hemolysis and fibrinolysis are possible. Changes in plasma factors related to these potential complications of transcervical resection of the endometrium were measured. STUDY DESIGN: In 101 patients undergoing transcervical resection of the endometrium sodium, ammonium, and coagulation factors were measured preoperatively and postoperatively at intervals. In the initial 30 patients glycine and 28 other amino acids were measured at the same intervals. The results were correlated with the patients' clinical status and operative parameters. RESULTS: Glycine and nine other amino acids and ammonia showed increased postoperative plasma levels; these changes were correlated with the absorption of the irrigating glycine solution and the development of hyponatremia. Minor activation of fibrinolysis and hemolysis was also seen. CONCLUSION: Nausea after transcervical resection of the endometrium with 1.5% glycine for irrigation may be partly explained by toxic effects of glycine and its secondary metabolites in addition to the effects of water intoxication and hyponatremia. Minor, clinically insignificant changes in the coagulation system may also occur. Studies on alternatives to glycine for creation of near-isotonic irrigating solutions are encouraged.

Adult↗
PubMed2005

Decomposition of mixed malodorants in a wire-plate pulse corona reactor.

Decomposition characteristics of two groups of representative mixed malodorants (1, ethanethiol + hydrogen sulfide; 2, ethanethiol + ammonia) in air were investigated employing a wire-plate pulse corona reactor. A new type of high-voltage pulse generator with a thyratron switch and a Blumlein pulse-forming network (BPFN) was used in our experiments. The experiments were conducted at a gas-flow rate of 13 m3/h. Important parameters, including peak voltage, chemical structures of malodorants, pulse frequency, and initial concentration, which influenced the removal efficiency, were investigated. The results showed that the mixed malodorants could be treated effectively by pulse corona. The removal efficiencies of 200 mg/m3 C2H5SH and 200 mg/m3 H2S for group 1 were 95.6% and 100%, respectively, which were almost equal to those of the two pollutants separately. The energy cost was about 65.1-81.4 J/L, which was 31.5-45.2% lower than for treating pollutants alone. The removal efficiencies of 105 mg/m3 C2HsSH and 40 mg/m3 NH3 for group 2 were 93.1% and almost 100%, and the energy cost was 65.1 J/L, 55.6% lower than that which was treated separately. In the case of two groups of mixed malodorants removal, NOx, 03, SO2, CO2, and CO were all observed. Moreover, some sulfur and white crystal ammonium nitrates were discovered adhering to the corona wires in the removal of groups 1 and 2, respectively. A dynamics model was developed to describe the relation of the removal efficiency with specific energy density and initial concentration. In the case of group 1 removal,the decomposition rate constants decreased as compared to the single treating. As for group 2 removal, the decomposition rate constants increased, especially for NH3. According to the results, the optimization design for the reactor and the matching of high pulse voltage source can be reckoned.

Air Pollutants↗
PubMed2004

Isolation of thermophilic ammonium-tolerant bacterium and its application to reduce ammonia emission during composting of animal wastes.

A thermophilic bacterium, strain TAT105, was isolated from compost made of animal wastes. TAT105 had high tolerance to ammonium nitrogen up to 1200 mM, and highly assimilated nitrogen during the growth on swine feces. The strain was classified into Bacillus, close to Bacillus pallidus. To evaluate the effect of adding TAT105 to ammonia (NH3) emission during the composting process of animal wastes, laboratory scale composting was done. NH3 emission tended to be lower and nitrogen loss was smaller in the TAT105-added material than in the control material to which TAT105 was not added. Thermophilic ammonium-tolerant bacteria in the TAT105-added material increased to about 8x10(9) CFU/g of dry matter on the average during the tests, and most of them were judged to be TAT105 from morphological colony discrimination. These results suggested the possibility of reducing NH3 emission from composting of animal wastes by adding TAT105.

Agriculture↗
PubMed2004

Chemical inhibition of nitrification in activated sludge.

Conventional aerobic nitrification was adversely affected by single pulse inputs of six different classes of industrially relevant chemical toxins: an electrophilic solvent (1-chloro-2,4-dinitrobenzene, CDNB), a heavy metal (cadmium), a hydrophobic chemical (1-octanol), an uncoupling agent (2,4-dinitrophenol, DNP), alkaline pH, and cyanide in its weak metal complexed form. The concentrations of each chemical source that caused 1 5, 25, and 50% respiratory inhibition of a nitrifying mixed liquor during a short-term assay were used to shock sequencing batch reactors containing nitrifying conventional activated sludge. The reactors were monitored for recovery over a period of 30 days or less. All shock conditions inhibited nitrification, but to different degrees. The nitrate generation rate (NGR) of the shocked reactors recovered overtime to control reactor levels and showed that it was a more sensitive indicator of nitrification inhibition than both initial respirometric tests conducted on unexposed biomass and effluent nitrogen species analyses. CDNB had the most severe impact on nitrification, followed by alkaline pH 11, cadmium, cyanide, octanol, and DNP. Based on effluent data, cadmium and octanol primarily inhibited ammonia-oxidizing bacteria (AOB) while CDNB, pH 11,and cyanide inhibited both AOB and nitrite-oxidizing bacteria (NOB). DNP initially inhibited nitrification but quickly increased the NGR relative to the control and stimulated nitrification after several days in a manner reflective of oxidative uncoupling. The shocked mixed liquor showed trends toward recovery from inhibition for all chemicals tested, but in some cases this reversion was slow. These results contribute to our broader effort to identify relationships between chemical sources and the process effects they induce in activated sludge treatment systems.

1-Octanol↗
PubMed2003

Ammonium utilization in Bacillus subtilis: transport and regulatory functions of NrgA and NrgB.

Bacillus subtilis uses glutamine as the best source of nitrogen. In the absence of glutamine, alternative nitrogen sources such as ammonium can be used. Ammonium utilization involves the uptake of the gas or the ammonium ion, the synthesis of glutamine by the glutamine synthetase and the recycling of the glutamate by the glutamate synthase. In this work, ammonium transport in B. subtilis was studied. At high ammonium concentrations, a large fraction of the ammonium is present as ammonia, which may enter the cell via diffusion. In contrast, the ammonium transporter NrgA is required for ammonium utilization at low concentrations or at low pH values when the equilibrium between uncharged ammonia and the ammonium ion is shifted towards ammonium. Moreover, a functional NrgA is essential for the transport of the ammonium analogue methylammonium. NrgA is encoded in the nrgAB operon. The product of the second gene, NrgB, is a member of the PII family of regulatory proteins. In contrast to PII proteins from other organisms, there is no indication for a covalent modification of NrgB in response to the nitrogen supply of the cell. It is demonstrated here that NrgB is localized at the membrane, most likely in association with the ammonium transporter NrgA. The presence of a functional NrgB is required for full-level expression of the nrgAB operon in response to nitrogen limitation, suggesting that NrgB might relay the information on ammonium availability to downstream regulatory factors and thus fine-tune their activity.

Bacillus subtilis↗
PubMedDate not supplied

[The hyperbaric oxygen therapy of disordered ammonia detoxication in the operated liver].

The status of the main routes of ammonium detoxication in the liver (synthesis of glutamine and urea) after its resection and hyperbaric oxygenation (HBO) was studied in 160 rats. HBO (3 sessions at 3 atm. abs.--50 min) following resection of the liver stimulated the activity of glutamine synthase and prevented the reduction of glutamate (a substrate for glutamine synthesis) level in the operated on liver. Hyperbaric oxygen activated the glutamine-dependent and non-glutamine-dependent pathways of urea synthesis in the resected liver and ensured the incorporation of glutamine amido groups in the ornithine cycle. HBO boosted the inhibitory effect of liver resection on the activity of glutamate dehydrogenase and prevented the accumulation of ammonium in the hepatocytes of resected liver. The stimulating effect of HBO on the ammonium-detoxifying function of the resected liver persisted for 11 days after the exposure.

Animals↗
PubMed1986

Ammonia toxicity: comparative protective effect of various arginine and ornithine derivatives, aspartate, benzoate, and carbamyl glutamate.

Ornithine and arginine compounds were highly effective in preventing an increase in blood ammonia and in preventing or minimizing encephalopathy after acute subcoma, coma-inducing, or lethal doses of NH4+. Similar protection was seen after subacute loading with glycine. Ornithine ketoacid derivatives were no more effective than ornithine alone or ornithine glutamate. Ornithine appeared to be a little more effective than arginine, but the differences were slight. Aspartate and glutamate alone were ineffective. Carbamyl glutamate was much less effective than either ornithine glutamate or arginine glutamate. Orotic acid excretion was markedly increased in the presence of excess NH4+. This increment was eliminated with ornithine or arginine, although the reduction with arginine was unpredictably erratic. Aspartate increased the orotic acid excretion and the amount of urea formed. Sodium benzoate was borderline in its effect on the blood ammonia and on orotic acid excretion.

Ammonia↗
PubMed2006

Spike-wave stupor in a patient with metabolic disorder.

We report a 79-year-old woman with a decreased level of consciousness. Investigation revealed an elevated serum ammonia and a portal-systemic shunt on angiography. Thus, her symptoms were thought to be due to metabolic encephalopathy. Her electroencephalogram (EEG) showed bilaterally synchronous runs of three-phase waves consistent with the triphasic waves typically seen in metabolic encephalopathy. However, after intravenous administration of diazepam, the EEG abnormalities improved; indicating that her decreased consciousness was of epileptic etiology, consistent with spike-wave stupor. Therefore, even in the presence of a clearly defined metabolic disorder, triphasic waves on the EEG may not be due to metabolic encephalopathy; they may reflect an epileptic state precipitated by the metabolic disorder.

Aged↗
PubMed1997

Determination of hexahydrophthalic acid and methylhexahydrophthalic acid in plasma after derivatisation with pentafluorobenzyl bromide using gas chromatography and mass spectrometric detection.

A method for the simultaneous determination of hexahydrophthalic acid (HHP acid) and methylhexahydrophthalic acid (MHHP acid) in human plasma was developed. The procedure was a rapid, single step extractive derivatisation with pentafluorobenzyl bromide as the derivatisation agent. The formed pentafluorobenzyl esters were analysed by gas chromatography-mass spectrometry in negative ion chemical ionisation mode with ammonia as the moderating gas. Deuterium-labeled HHP acid and MHHP acid were used as internal standards. The detection limit was 0.4 ng/ml for HHP acid (m/z 153) and 0.3 ng/ml for MHHP acid (m/z 365). The within-day precision of the method was between 2 and 3% and the between-day precision was between 3 and 12%. The overall recovery was between 65 and 83%. A comparison between HHP acid determinations with a previous and this method showed that the methods gave similar results. The method was applicable for analysis of plasma from occupationally exposed workers.

Cyclohexanecarboxylic Acids↗
PubMed2006

Theoretical characterization of end-on and side-on peroxide coordination in ligated Cu2O2 models.

The relative energetics of mu-eta1:eta1 (trans end-on) and mu-eta2:eta2 (side-on) peroxo isomers of Cu2O2 fragments supported by 0, 2, 4, and 6 ammonia ligands have been computed with various density functional, coupled-cluster, and multiconfigurational protocols. There is substantial disagreement between the different levels for most cases, although completely renormalized coupled-cluster methods appear to offer the most reliable predictions. The significant biradical character of the end-on peroxo isomer proves problematic for the density functionals, while the demands on active space size and the need to account for interactions between different states in second-order perturbation theory prove challenging for the multireference treatments. In the latter case, it proved impossible to achieve any convincing convergence.

Cations, Divalent↗
PubMed1977

Nitrogen regulation of arginase in Neurospora crassa.

The final products of the arginine catabolism that can be utilized as a nitrogen source in Neurospora crassa are ammonium, glutamic acid, and glutamine. The effect of these compounds on arginase induction by arginine was studied. In wild-type strain 74-A, induction by arginine was almost completely repressed by glutamic acid plus ammonium, whereas ammonium or glutamic acid alone had only moderate effects. Arginine products of catabolism also repressed arginase induction. A mutant, ure-1, which lacks urease activity, hyperinduced its arginase with arginine as a nitrogen source. The addition of either ammonium or glutamine produced effects similar to those in the wild-type strain. The effect of ammonium on arginase induction is mediated through its conversion into glutamine. This was demonstrated in mutant am-1, which lacks L-glutamate dehydrogenase activity. In this mutant, the effect of glutamic acid was reduced, and, with ammonium, it was completely lost. The addition of glutamine or glutamic acid plus ammonium to this strain decreased by threefold the induction of arginase by arginine. Proline, a final product of arginine catabolism, competitively inhibited arginase activity. This effect and the repression of arginase by glutamine are examples of negative modulation of the first enzyme in a catabolic pathway by its final products.

Ammonia↗
PubMed2004

Treatment of nitrogen and phosphorus in highly concentrated effluent in SBR and SBBR processes.

Various sludge treatment processes produced supernatant with high ammonia concentration from 500 to 2,000 mgN/L and generally high phosphate concentration. Conversion of ammonia into nitrite via partial nitrification has proven to be an economic way, reducing oxygen and external COD requirements during the nitrification/denitrification process. Two processes with biomass retention are studied simultaneously: the sequencing batch reactor (SBR) and the sequencing batch biofilm reactor (SBBR). At a temperature of 30 degrees C, the inhibition of nitrite-oxidizing bacteria due to high ammonia concentration has been studied in order to obtain a stable nitrite accumulation. This work has confirmed the effect of pH and dissolved oxygen on nitrite accumulation performance. During a two month starting period, both processes led to nitrite accumulation without nitrate production when pH was maintained above 7.5. From a 500 mgN/L effluent, the performance of the SBR, and the SBBR, reached respectively about 0.95gN-NO2-/gN-NH4+, and 0.4gN-NO2-/gN-NH4+. The SBBR appears to be more stable facing disturbances in dissolved oxygen conditions. Finally, the maximal phosphate removal rates obtained in the SBR reached 90%, and 70% in the SBBR, depending on ammonium accumulation in the reactor. Ammonium phosphate precipitation is likely to occur, as was suggested by crystals observation in the reactor.

Biofilms↗
PubMed2003

The active conformation of glutamate synthase and its binding to ferredoxin.

Glutamate synthases (GltS) are crucial enzymes in ammonia assimilation in plants and bacteria, where they catalyze the formation of two molecules of L-glutamate from L-glutamine and 2-oxoglutarate. The plant-type ferredoxin-dependent GltS and the functionally homologous alpha subunit of the bacterial NADPH-dependent GltS are complex four-domain monomeric enzymes of 140-165 kDa belonging to the NH(2)-terminal nucleophile family of amidotransferases. The enzymes function through the channeling of ammonia from the N-terminal amidotransferase domain to the FMN-binding domain. Here, we report the X-ray structure of the Synechocystis ferredoxin-dependent GltS with the substrate 2-oxoglutarate and the covalent inhibitor 5-oxo-L-norleucine bound in their physically distinct active sites solved using a new crystal form. The covalent Cys1-5-oxo-L-norleucine adduct mimics the glutamyl-thioester intermediate formed during L-glutamine hydrolysis. Moreover, we determined a high resolution structure of the GltS:2-oxoglutarate complex. These structures represent the enzyme in the active conformation. By comparing these structures with that of GltS alpha subunit and of related enzymes we propose a mechanism for enzyme self-regulation and ammonia channeling between the active sites. X-ray small-angle scattering experiments were performed on solutions containing GltS and its physiological electron donor ferredoxin (Fd). Using the structure of GltS and the newly determined crystal structure of Synechocystis Fd, the scattering experiments clearly showed that GltS forms an equimolar (1:1) complex with Fd. A fundamental consequence of this result is that two Fd molecules bind consecutively to Fd-GltS to yield the reduced FMN cofactor during catalysis.

Crystallography, X-Ray↗
PubMed2004

Preparation of solid drug/cyclodextrin complexes of acidic and basic drugs.

One of the main obstacles in pharmaceutical applications of cyclodextrins is their increase of the formulation bulk. Even at maximum incorporation 500 mg of a solid drug/cyclodextrin complex will only contain between 50 and 125 mg of the drug, assuming a low molecular weight drug (MW 200 to 400 Dalton) and an average molecular weight cyclodextrin (MW about 1500 Dalton). In general, the complexation efficiency is low and consequently the complex powder contains a significant amount of empty cyclodextrin molecules. In the present study the complexation efficiency is increased by ionization of the drug molecule through addition of volatile acid (i.e. acetic acid) or base (i.e. ammonia) to the aqueous complexation media of basic or acidic drugs, respectively. The volatile acid or base was then removed during lyophilization and heating in a vacuum oven resulting in formation of solid cyclodextrin complexes of the unionized drug. Thus, the complexation efficiency was temporary increased by the ionization but then again decreased leading to formation of the thermodynamically unstable solid drug/cyclodextrin complexes. When dissolved the energy of the system was lowered by expelling the drug molecules from the cyclodextrin cavities resulting in formation of supersaturated drug solutions and ultimately precipitation of the drug.

Acetates↗
PubMedDate not supplied

[Peculiarities of DNA winding with bifunctional cations].

Addition of the bifunctional cations, bis(2-aminoethyl) disulphide-cystamine, and bis(2-guanidoethyl) disulphide-GED, into water solution of DNA results in a decrease in magnitude of the positive circular dichroism (CD) band. However, unlike the similar effect due to alcaline ions or ions of ammonium and guanidinium the above effect occurs at much smaller, stoichiometric with phosphates, concentrations of the dications. Another peculiarity of GED is the attaining of a plato region for the curve of the CD change with the rise of GED concentration. Since the decrease in positive band CD is connected with increase in the rotation angle between the base pairs, the observed behavior of the bifunctional cations are supposedly due to peculiarities of their winding action upon DNA helix. Reducing the disulphide bond in the cations gives rise to increase in the DNA positive CD band up to the values inherent to those in the presence of the corresponding monocations. The higher efficiency of the bifunctional cations is thus due to the cationic groups belong to one and the same molecule. Such compounds could thus be considered as a simple model of DNA-protein interaction.

Ammonia↗