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PubMed1980

Increase of nitrogenase activity in the blue-green alga Nostoc muscorum (Cyanobacterium).

Preincubation of the blue-green alga (cyanobacterium) Nostoc muscorum under hydrogen or argon (nongrowing conditions, neither CO(2) nor N(2) or bound nitrogen present) in the light resulted in a two- to fourfold increase of light-induced hydrogen evolution and a 30% increase of acetylene reduction. Preincubation under the same gases in the dark led to a decrease of both activities. Cultivation of algae under a hydrogen-containing atmosphere (N(2), H(2), CO(2)) increased neither hydrogen nor ethylene evolution by the cells. Formation of both ethylene and hydrogen is due to nitrogenase activity, which apparently was induced by the absence of N(2) or bound nitrogen and not by the presence of hydrogen. Inhibitors of protein biosynthesis prevented the increase of nitrogenase activity. Hydrogen uptake by the cells was almost unaffected under all of these conditions. With either ammonia or chloramphenicol present, nitrogenase activity decreased under growing conditions (i.e., an atmosphere of N(2) and CO(2)). The kinetics of decrease were the same with ammonia or chloramphenicol, which was interpreted as being due to rapid protein breakdown with a half-life of approximately 4 h. The decay of nitrogenase activity caused by chloramphenicol could be counteracted by nitrogenase-inducing conditions, i.e., by the absence of N(2) or bound nitrogen. A cell-free system from preconditioned algae with an adenosine 5'-triphosphate-generating system exhibited the same increase or decrease of nitrogenase activity as the intact cell filaments, indicating that this effect resided in the nitrogenase complex only. We tentatively assume that not the whole nitrogenase complex, but merely a subunit or a special protein with regulatory function, is susceptible to fast turnover.

Acetylene↗
PubMed1983

Neurospora crassa mutant impaired in glutamine regulation.

The final products of the catabolism of arginine that can be utilized as nitrogen sources by Neurospora crassa are ammonium, glutamic acid, and glutamine. Of these compounds, only glutamine represses arginase and glutamine synthetase. We report here the isolation and characterization of a mutant of N. crassa whose arginase, glutamine synthetase, and amino acid accumulations are resistant to glutamine repression (glnI). This mutant has a greater capacity than the wild type (glns) to accumulate most of the arginine and some of the glutamine in osmotically sensitive compartments while growing exponentially. Nonetheless, the major part of the glutamine remains soluble and metabolically available for repression. We propose that the lower repression of glutamine synthetase by glutamine in this mutant could be a necessary condition for sustaining the higher flow of nitrogen for the accumulation of amino acids observed in ammonium excess and that, if glutamine is the nitrogen signal that regulates the arginine accumulation of the vesicle, the glnr mutant has also escaped this control. Finally, in the glnr mutant, some glutamine resynthesis is necessary for arginine biosynthesis and accumulation.

Amino Acids↗
PubMedDate not supplied

The in vitro efficacy of a quaternary ammonia disinfectant and/or ethylenediaminetetraacetic acid-tris against commercial broiler hatchery isolates of Pseudomonas aeruginosa.

Studies have indicated variations in the degree of efficacy of certain commercial disinfectants used in poultry production facilities. We used an adequate method of in vitro testing to compare the efficacy of disinfectants while testing them in conditions similar to those of the poultry facilities. BioSentry 904, ethylenediaminetetracetic acid (EDTA)-Tris, and a combination of the two were tested by this method against five field isolates of Pseudomonas aeruginosa at 10(3), 10(6), and 10(9) colony-forming units (CFU)/ml. At the 10(9) CFU/ml concentration, most compounds failed to achieve a total kill with a contact time of 15 min. When tested at bacterial concentrations of 10(3) CFU/ml, the combination of EDTA-Tris mixed at a 1:1 ratio with BioSentry 904 killed the bacteria upon initial contact (< or = 0.05 min). This disinfectant mixture exhibited antagonistic, indifferent, or synergetic effects when exposed to different bacterial isolates at a concentration of 10(6) CFU/ml.

Animals↗
PubMed1981

Regulation of urease and ammonia assimilatory enzymes in Selenomonas ruminantium.

Urease and glutamine synthetase activities in Selenomonas ruminantium strain D were highest in cells grown in ammonia-limited, linear-growth cultures or when certain compounds other than ammonia served as the nitrogen source and limited the growth rate in batch cultures. Glutamate dehydrogenase activity was highest during glucose (energy)-limited growth or when ammonia was not growth limiting. A positive correlation (R = 0.96) between glutamine synthetase and urease activities was observed for a variety of growth conditions, and both enzyme activities were simultaneously repressed when excess ammonia was added to ammonia-limited, linear-growth cultures. The glutamate analog methionine sulfoximine (MSX), inhibited glutamine synthetase activity in vitro, but glutamate dehydrogenase, glutamate synthase, and urease activities were not affected. The addition of MSX (0.1 to 100 mM) to cultures growing with 20 mM ammonia resulted in growth rate inhibition that was dependent upon the concentration of MSX and was overcome by glutamine addition. Urease activity in MSX-inhibited cultures was increased significantly, suggesting that ammonia was not the direct repressor of urease activity. In ammonia-limited, linear-growth cultures, MSX addition resulted in growth inhibition, a decrease in GS activity, and an increase in urease activity. These results are discussed with respect to the importance of glutamine synthetase and glutamate dehydrogenase for ammonia assimilation under different growth conditions and the relationship of these enzymes to urease.

Ammonium Chloride↗
PubMed2002

Determination of inorganic cations and ammonium in environmental waters by ion chromatography with a high-capacity cation-exchange column.

While alkali and alkaline earth cations are commonly determined by using spectrometric techniques such as atomic absorption spectrometry or inductively coupled plasma, ammonium cation in the same sample must be measured separately by a wet chemical technique such as colorimetry, titrimetry, or ammonia-selective electrode. In a single 25-min run ion chromatography can determine all of the important inorganic cations including lithium, sodium, ammonium, potassium, magnesium and calcium. In this paper, we describe the use of ion chromatography with a new high-capacity cation-exchange column (the IonPac CS16), an electrolytically-generated methanesulfonic acid eluent and suppressed conductivity detection to determine dissolved alkali and alkaline earth cations and ammonium in drinking water wastewater and aqueous soil extracts. The IonPac CS16 is a high-capacity cation-exchange column that incorporates recent advances in polymer chemistry to enable trace-level determinations of cations even in high-ionic-strength matrices. We discuss the linear range, method detection limits, and analyte recoveries obtained with this column, and evaluate the effect of potential interferences on method performance during the analysis of typical environmental samples.

Cation Exchange Resins↗
PubMed1994

Cl(-)-dependent NH4+ transport mechanisms in medullary thick ascending limb cells.

To characterize Cl(-)-dependent NH4+ transport mechanisms in renal medullary thick ascending limb (MTAL), intracellular pH (pHi) and membrane potential (PD) were monitored with use of 2',7'-bis(carboxyethyl)- 5(6)-carboxyfluorescein and 3,3'-dipropylthiadicarbocyanine, respectively, in suspensions of rat MTAL tubules in CO2-free media. Exposure of MTAL cells to 4 mM NH4Br caused, after an initial cell alkalinization due to NH3 entry, an NH4(+)-induced fall in pHi that was approximately 67% less pronounced in Cl(-)-free than in Cl(-)-containing media. The following experiments were performed in the presence of 1 microM amiloride to block the MTAL NH4+ conductance. When cells were preincubated in a Cl(-)-free gluconate medium in which K+ and Cl- conductances are greatly reduced, abrupt addition of 100 mN N-methyl-D-glucamine (NMDG)-Cl had no effect on cell PD and pHi in the absence of ammonia, but acutely acidified the cells by approximately 0.2 pH units in the presence of 4 mM NH4Br, which thus indicated nonelectrogenic (NMDG-Cl)-dependent NH4+ influx. The latter also occurred in a Cl(-)-free thiocyanate medium in which the Cl- conductance was blocked by 0.1 mM diphenylamine-2-carboxylate (DPC). An NMDG-Cl- dependent NH4(+)-induced fall in pHi was reduced approximately 33% by 10 mM Ba+, approximately 84% by 0.1 mM bumetanide, and 100% by 1.5 mM furosemide, whereas 1 mM hydrochlorothiazide had no effect; inhibition by Ba+ was observed even in the presence of 0.1 mM verapamil added to block both K+ channels and K+/NH4+ antiport.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

Optimalisation of magnesium ammonium phosphate precipitation and its applicability to the removal of ammonium.

Among the physico-chemical abatement technologies, mainly acid scrubbers have been used to control NH3-emission. The disadvantage of this technique is that it yields waste water, highly concentrated in ammonia. In this report, the applicability of the magnesium ammonium phosphate (MAP) process to regenerate the liquid phase, produced by scrubbing NH3-loaded waste gases, was investigated. In the MAP process, ammonium is precipitated as magnesium ammonium phosphate, which can be used as a slow release fertilizer. The influence of a number of parameters, e.g. pH, kinetics, molar ratio NH(+)4/Mg2+/PO(3-)4 on the efficiency of the formation of MAP and on the ammonium removal efficiency was investigated. In this way, optimal conditions were determined for the precipitation reaction. Next to this, interference caused by other precipitation reactions was studied. At aqueous NH(+)4-concentrations of about 600 mg l(-1), ammonium removal efficiencies of 97% could be obtained at a molar ratio NH(+)4/Mg2+/PO(3-)4 of 1/1.5/1.5. To obtain this result, the pH was continuously adjusted to a value of 9 during the reaction. According to this study, it is obvious that the MAP-precipitation technology offers opportunities for ammonium removal from scrubbing liquids. The practical applicability of the MAP-process in waste gas treatment systems, however, should be the subject for further investigations.

Chemical Precipitation↗
PubMed2000

Differential regulation of amoA and amoB gene copies in Nitrosomonas europaea.

Nitrosomonas europaea contains two nearly identical copies of the operon, amoCAB, which encodes the ammonia monooxygenase (AMO) enzyme. Cells of N. europaea containing single mutations in either amoA or amoB gene copies were incubated in ammonium both prior to and after exposure to acetylene or light. For each strain, the O(2) consumption rates and amounts of AmoA polypeptide, the active site-containing subunit of AMO, produced in each strain were determined. Strains carrying a mutation in either the amoA(2) or amoB(2) genes responded similarly to wild-type cells, but the strains carrying mutations in the amoA(1) or amoB(1) genes responded differently from the wild-type, or from each other. These results suggest that the copies of amoA and amoB are differentially regulated upon exposure to different external stimuli.

Acetylene↗
PubMed2005

Nitrification performance and microbial community dynamics in a submerged membrane bioreactor with complete sludge retention.

A submerged membrane bioreactor (MBR) supplied with inorganic ammonium-bearing wastewater (NH(4)(+)-N, 500 mgl(-1)) was operated for 260 days without sludge purge under decreased hydraulic retention times (HRT) through six steps (from 30 to 5h). Almost complete nitrification was obtained at a volumetric loading rate (VLR)1.2g NH(4)(+)-Nl(-1)day(-1). The sludge nitrification activities were evaluated at each stage. The specific ammonium oxidizing rate (SAOR) decreased from the initial 0.45 to 0.15 kg NH(4)(+)-Nkg(-1)MLSSday(-1) in the last four stages, while the specific nitrate forming rate (SNFR) increased from 0.17 to 0.39 kg NO(3)(-)-Nkg(-1)MLSSday(-1) at the third stage, and then decreased to below 0.1 kg NO(3)(-)-Nkg(-1)MLSSday(-1) from the fourth stage. Microbial population dynamics was investigated by a combination of the MPN method, fluorescence in situ hybridization (FISH) and quinone profiles. During the experiment, although the MLSS increased gradually from 4.5 to 11.5 gl(-1), the number of ammonia-oxidizing bacteria (AOB) decreased from 10(9)l(-1) at the third stage to 10(7)l(-1) in the last two stages, and that of nitrite-oxidizing bacteria (NOB) decreased gradually from 10(8)l(-1) at the second stage (HRT of 20 h) to the final 10(5)l(-1). FISH results showed that the active cells decreased gradually with time from about 60 to 20% in the last two stages, and most of sludge was inert cells. The sum of nitrifiers occupied only about 10% of the total bacteria number in the last stage even though only ammonium-bearing inorganic wastewater was fed in. Nitrosomonas sp. and Nitrospira sp. were confirmed by FISH as the dominant nitrifying genera responsible for ammonia and nitrite oxidation, respectively. In the mean time, a small ratio of Nitrobacter sp. also existed in the system. FISH analysis matched better with the batch activity test results than did the MPN techniques. Quinone profiles revealed that the dominant ubiquinone was ubiquinone-8 (UQ-8), ranging from 84 to 66%, followed by UQ-10 of 7-13%, UQ-7 of 3-5% and UQ-9 of 1.6-2.6%. The dominant menaquinone in the MBR was menaquinone-7 (MK-7) followed by MK-6, MK-8 and MK-8 (H(2)). With the prolongation of operation, the percentage of menaquinones increased from 8 to 14%. The use of the polyphasic approach gave some new insight on variations of microbial community structures.

Bacteria↗
PubMed2002

Determination of the 15N/14N ratio of ammonium and ammonia in aqueous solutions by equilibrium headspace-gas chromatography-combustion-isotope ratio mass spectrometry.

A method for determination of the 15N/14N ratio of total ammoniacal nitrogen (TAN; ammonium and ammonia) in aqueous solutions was developed, primarily intended for use with soil extracts, which have a high TAN level, e.g. from recently fertilised agricultural soils. Ammonium was converted to ammonia by addition of NaOH, followed by nitrogen isotopic analysis of the headspace by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) where complete separation of TAN from the matrix was not necessary. The ammonia concentration in the gas phase was maximised by increasing the temperature and salt concentration and by decreasing the gas liquid ratio in the headspace vials. Isotopic equilibrium was reached after less than 1 h at 80 degrees C. The measured isotopic ratio was constant for solutions containing 30-200 mM NH4-N, corresponding to 950-7000 ng NH3-N detected with the IRMS. The integrated area response at m/z 28 increased linearly with the ammonium ion concentration in the interval 10-200 mM NH4-N. The fractionation factor between the liquid and gas phases was 1.0054 +/- 0.0007 within the linear range, which is in agreement with values reported in the literature, but with a higher precision. Changes in temperature, gas:liquid ratio or salt concentration did not affect the measured ratio, demonstrating the robustness of the developed method.

Chromatography, Gas↗
PubMed1975

Ultraviolet-gas phase and -photocatalytic synthesis from CO and NH3.

The major photoproduct obtained on irradiation of gaseous NH3 and CO mixtures is ammonium cyanate; lesser amounts of urea, biurea, biuret semi-carbazide, formamide and cyanide were observed. The formation of the major gas phase photolysis product may be rationalized by the following reaction sequence: (see article). Urea is probably formed from NH4NCO in a thermal reaction while formamide may result from the disproportionation of NH2CO. Photocatalytic syntheses of 14C-urea, -formamide, and -formadehyde are effected by irradiation of 14CO and NH3 in the presence of Vycor, silica gel, or volcanic ash shale surfaces. These syntheses are catalyzed by ultraviolet wavelengths longer than those absorbed by the gaseous reactants. The syntheses are also effected when the surface material is first irradiated in the presence of CO followed by a dark incubation with NH3. Apparently, the initiating step is a light dependent formation of a reactive form of CO on the surface. A discussion is given on the possible contribution of these reactions to the abiotic synthesis of organic nitrogen compounds on Mars, on the primitive Earth and in interstellar space.

Ammonia↗
PubMed1990

Control of nitrogenase recovery from oxygen inactivation by ammonia in the cyanobacterium Anabaena sp. strain CA (ATCC 33047).

The control of nitrogenase recovery from inactivation by oxygen was studied in Anabaena sp. strain CA (ATCC 33047). Nitrogenase activity (acetylene reduction) in cultures grown in 1% CO2 in air was inhibited by exposure to 1% CO2-99% O2 and allowed to recover in the presence of high oxygen tensions. Cultures exposed to hyperbaric levels of oxygen in the presence of 10 mM NH4NO3 were incapable of regaining nitrogenase activity, whereas control cultures returned to 65 to 80% of their original activity within about 3 h after exposure to high oxygen tension. In contrast to the regulation of heterocyst differentiation and nitrogenase synthesis, recovery from oxygen inactivation in this organism was shown to be under the control of NH4+ rather than NO3-.

Ammonium Chloride↗
PubMed2004

Nitrogen removal from sludge water with SBR process: start-up of a full-scale plant in the municipal wastewater treatment plant at Ingolstadt, Germany.

The sludge water obtained from the dewatering processes following anaerobic sludge digestion contains high levels of ammonia. This sludge water is generally returned to the beginning of the waste water treatment plant process, thereby significantly increasing the nitrogen load on the biological process. In this project, the start-up of a full-scale sequencing batch reactor (SBR) process to separately treat the aforementioned sludge water is studied. Two parallel SBRs were operated over 8 hour cycles. The duration of the start-up was approximately 100 days until a hydraulic load of 225 m3/d was reached for each SBR. This paper presents the results of the start-up, highlighting the change in nitrogen concentration with time and the effect of other parameters such as temperature and suspended solids in that period. Following the project period of operation, the ammonium concentration was reduced by more than 95% on average.

Biofilms↗
PubMed1998

Prebiotic amino acid thioester synthesis: thiol-dependent amino acid synthesis from formose substrates (formaldehyde and glycolaldehyde) and ammonia.

Formaldehyde and glycolaldehyde (substrates of the formose autocatalytic cycle) were shown to react with ammonia yielding alanine and homoserine under mild aqueous conditions in the presence of thiol catalysts. Since similar reactions carried out without ammonia yielded alpha-hydroxy acid thioesters (Weber, 1984a, b), the thiol-dependent synthesis of alanine and homoserine is presumed to occur via amino acid thioesters--intermediates capable of forming peptides (Weber and Orgel 1979). A pH 5.2 solution of 20 mM formaldehyde, 20 mM glycolaldehyde, 20 mM ammonium chloride, 23 mM 3-mercaptopropionic acid, and 23 mM acetic acid that reacted for 35 days at 40 degrees C yielded (based on initial formaldehyde) 1.8% alanine and 0.08% homoserine. In the absence of thiol catalyst, the synthesis of alanine and homoserine was negligible. Alanine synthesis required both formaldehyde and glycolaldehyde, but homoserine synthesis required only glycolaldehyde. At 25 days the efficiency of alanine synthesis calculated from the ratio of alanine synthesized to formaldehyde reacted was 2.1%, and the yield (based on initial formaldehyde) of triose and tetrose intermediates involved in alanine and homoserine synthesis was 0.3 and 2.1%, respectively. Alanine synthesis was also seen in similar reactions containing only 10 mM each of aldehyde substrates, ammonia, and thiol. The prebiotic significance of these reactions that use the formose reaction to generate sugar intermediates that are converted to reactive amino acid thioesters is discussed.

Acetaldehyde↗
PubMed1983

Role of glutamine synthetase in the uptake and metabolism of methylammonium by Azotobacter vinelandii.

Methylammonium is a substrate for the ammonium transport system of Azotobacter vinelandii. During cellular uptake methylammonium is rapidly converted to a less polar metabolite (E. M. Barnes, Jr., and P. Zimniak, J. Bacteriol. 146:512-516, 1981). This metabolite has been isolated from A. vinelandii and identified as gamma-glutamylmethylamide by mass spectroscopy, 1H nuclear magnetic resonance spectroscopy, and cochromatography with the authentic compound. Escherichia coli also accumulated gamma-glutamylmethylamide during methylammonium uptake. The biosynthesis of gamma-glutamylmethylamide in vitro required methylammonium, ATP, L-glutamate, and a soluble cell extract from A. vinelandii. The enzyme responsible for gamma-glutamylmethylamide synthesis was glutamine synthetase. In a crude extract, L-methionine-DL-sulfoximine was equipotent in inhibiting the activities for gamma-glutamyltransferase and for the synthesis of glutamine and gamma-glutamylmethylamide. Likewise, an antiserum against the glutamine synthetase of E. coli precipitated the transferase and both synthetic activities at similar titers. During repression by growth of cells on ammonium medium, the synthesis of glutamine and gamma-glutamylmethylamide in vitro was also inhibited coordinately. A partially purified preparation of glutamine synthetase from A. vinelandii utilized methylammonium as substrate (Km = 78 mM, Vmax = 0.30 mumol/min per mg), although less efficiently than ammonium (Km = 0.089 mM, Vmax = 1.1 mumol/min per mg). The kinetic properties of glutamine synthetase with methylammonium as substrate as well as the insensitivity of this activity to inhibition by T1+ were strikingly different from methylammonium translocation. Thus, methylammonium (ammonium) translocation and intracellular trapping as glutamylamides are experimentally distinguishable processes.

Azotobacter↗
PubMed2003

Denitrification of nitrate by the fungus Cylindrocarpon tonkinense.

The denitrifying fungus Cylindrocarpon tonkinense was thought to be able to denitrify only nitrite (NO2-) but not nitrate (NO3-) to form nitrous oxide (N2O). Here we found, however, that C. tonkinense can denitrify NO3- under certain conditions. Presence of ammonium (NH3+) in addition to NO3- and the use of a fermentable sugar as an electron donor were key conditions for inducing the denitrifying activity. Such induction accompanied a remarkable increase in the intracellular level of the enzyme activities related to NO3- metabolism. These activities contained assimilatory type NADPH (or NADH)-dependent NO3- reductase (aNar), dissimilatory nitrite reductase (dNir), and nitric oxide reductase (P450nor), but did not contain ubiquinol-dependent, dissimilatory NO3- reductase (dNar). The denitrification was inhibited by tungstate, an inhibitor of Nar. These results demonstrated occurrence of a novel type of denitrification in C. tonkinense, in which assimilatory type Nar is possibly involved.

Ammonia↗
PubMed1982

Physiology of ammonium assimilation in Neurospora crassa.

In Neurospora crassa the assimilation of high and low concentrations of ammonium occurs by two different pathways. When the fungi are growing exponentially on ammonium excess, this compound is fixed by a glutamic dehydrogenase and an octameric glutamine synthetase (GS). The synthesis of this GS polypeptide (beta) is regulated by the nitrogen source present in excess; being higher on glutamate, intermediate on ammonium, and lower on glutamine. When N. crassa is growing in fed-batch ammonium-limited cultures a different polypeptide of GS (alpha), arranged as a tetramer, is synthesized. In both conditions synthesis in vivo correlates with the data obtained with an in vitro translation system primed with N. crassa RNA. This different expression of alpha and beta GS polypeptides was also observed when the cultures were shifted from excess to low nitrogen, and vice versa. By agarose gel electrophoresis in the presence of methylmercury hydroxide, some separation of different mRNAs that direct the in vitro synthesis of alpha and beta GS polypeptides has been accomplished. Data are presented that establish the operation of the tetrameric alpha GS and of glutamate synthase in the assimilation of ammonium in low concentration.

Ammonium Chloride↗
PubMed2004

Nitrification in natural waters with high suspended-solid content--a study for the Yellow River.

In this research, the mechanism regarding the effects of suspended solids on nitrification in freshwater systems with high solid contents was examined. Experimental studies were conducted for natural water of the Yellow River under laboratory conditions. Nitrification kinetics was investigated in water systems with various levels of suspended-solid contents. The associated mechanisms were analyzed through investigation of the adsorption-desorption of ammonium nitrogen, the process of bacteria growth, and the feature of nitrification kinetics. The results indicated that the presence of suspended solids could accelerate the nitrification process. The nitrification rate would increase non-linearly with the increase of suspended-solid content. When the initial concentration of ammonia nitrogen was 12.70 mg/l in the water system, the ratios of half-time duration for nitrification would be 1.88:1.23:1 under suspended-solid contents of 0, 1.84 and 5.00 g/l, respectively. When the initial concentration of ammonia nitrogen was around 1.0 mg/l in the water system, the nitrification rates in systems with suspended-solid contents of 1.81 and 3.42 g/l would then be approximately 9 and 12 times that without suspended solids, respectively. The populations of nitrifying bacteria would rise with increasing suspended-solid content. The existence of suspended solids would increase the contact chances between bacteria and nitrogen, resulting in accelerated nitrification processes; this was manifested by the increased K(4) (tau(max)/K(S)) along with the raised suspended-solid contents while fitting nitrification kinetics with the growth-based logistic model. Since the amount of ammonium nitrogen adsorbed on suspended-solid surface was non-linearly proportional to the suspended-solid content, the nitrification rate was also non-linearly proportional to the suspended-solid content.

Adsorption↗