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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 96 (1992), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A nicotinamide adenine dinucleotide-specific glutamate dehydrogenase (NAD-GluDH; EC 1.4.1.3) inactivated by incubation at low temperatures was detected in several species of the genus Bacillus, including strains of B. cereus, B. laterosporus, B. lentus, B. panthotenicus, B. pasteurii, B. sphaericus, B. stearothermophilus, B. subtilis and B. thuringiensis. Incubation of cell-free extracts of these strains at 0°C resulted in an 80–100% inactivation of NAD-GluDH activity within 120 min. The addition of 20% glucerol protected the enzyme from this inactivation in the cold. Strains of B. fastidiosus, B. licheniformis, B. macerans, B. megaterium and B. pumilus were found to lack NAD-GluDH activity.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 206 (2002), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In Bacillus pasteurii glutamine is being taken up efficiently by a sodium-dependent uptake system and subsequently hydrolysed to ammonium and glutamate. Concerning the latter process, a catabolic l-glutamine amidohydrolase (glutaminase) was isolated from the cytoplasm of this alkaliphilic bacterium and purified to homogeneity using liquid chromatography. Biochemical and physical parameters of the pure enzyme were examined in detail. Interestingly, analysis of the glutaminase revealed a marked increase in catalytic activity in the presence of phosphate, a property yet restricted to animal glutaminases. This is the first report on the presence of a phosphate-activated glutaminase in bacteria.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 72 (1990), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The mechanism of ammonium uptake was studied in Pseudomonas aeruginosa, measuring the uptake (transport and metabolism) of [14C]methylammonium (MA). This ammonium analogue was not utilized for growth, but unmetabolized MA was accumulated to intracellular concentrations about 30 times higher than those in the medium. Most of the MA taken up, however, was rapidly metabolized to β-N-methylglutamine, which could be removed from the cells by the addition of ammonium. Uptake of MA exhibited distinct optima at pH 7.0 and 35 to 40° C and depended on metabolis energy, as indicated by the inhibitory effect of various metabolic poisons. Growth with ammonium as nitrogen source resulted in the repression of MA uptake, whereas high uptake rates were observed with nitrate or after incubation without nitrogen source. These results suggested that the ammonium/MA uptake system is subject to nitrogen control in P. aeruginosa.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 57 (1989), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Evidence for the existence of an energy-dependent urea uptake system in Bacillus megaterium DSM 90 was obtained by studying the uptake of 14C-urea. In vivo urea uptake and in vitro urease activity differed significantly with respect to temperature- and pH-dependence, kinetic parameters and response towards metabolic inhibitors. Highest uptake activities were observed during exponential growth, and a rapid decrease in urea uptake occurred when cells entered the stationary growth phase and started to sporulate. Significant differences in the uptake rates were observed during growth with different nitrogen sources, suggesting that the formation of the system is under nitrogen control.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of polymers and the environment 7 (1999), S. 75-82 
    ISSN: 1572-8900
    Keywords: Methyleneureas ; fertilizer ; degradation ; ammonification ; nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The biodegradation of urea and condensation products thereof (ureaforms or methyleneureas), their nitrification, and their influence on the respiratory rate of soil was studied over periods of up to 100 days. The total methyleneurea content of the soil was determined after its acidic extraction, using a convenient colorimetric assay, and an HPLC protocol was established to analyze for specific components of methyleneureas. Urea, unfractionated methyleneureas, and hot-water soluble methyleneureas were rapidly metabolized to ammonium, which accumulated to high concentrations and was consequently oxidized to nitrate; an accumulation of nitrite was observed during urea but not during methyleneurea degradation. Hot water-insoluble methyleneureas were degraded much more slowly, and ammonium formed from these compounds was oxidized to nitrate without being released in significant amounts. These results suggest that the use of methyleneureas of optimized composition with regard to their water solubility may help to resolve problems such as the toxicity of ammonia to plant growth as well as nitrogen loss by leaching of nitrate, denitrification and volatilization.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of polymers and the environment 8 (2000), S. 11-16 
    ISSN: 1572-8900
    Keywords: Slow-release fertilizer ; methyleneureas ; microbial degradation ; Ralstonia paucula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Methyleneureas are condensation products of urea and formaldehyde of different molecular mass and solubility; they are used in large amounts both as resins, binders, and insulating materials for industrial applications, as well as a slow-release nitrogen fertilizer for greens, lawns, or in bioremediation processes. In the present study, the microbial breakdown of these products was investigated. The nitrogen was released as ammonia and urea, and the formaldehyde released immediately oxidized via formiate to carbon dioxide. The enzymatic mechanism of metabolization of methyleneureas was studied in microorganisms isolated from soil, which were able to use these compounds as the sole source of nitrogen for growth. A strain of the Gram-negative bacterium Ralstonia paucula (formerly Alcaligenes sp. CDC group IVc-2) completely degraded methylenediurea and dimethylenetriurea to urea, ammonia, formaldehyde, and carbon dioxide. The enzyme initiating this degradation (methylenediurease) was purified and turned out to be different from the previously described enzyme from Ochrobactrum anthropi with regard to its regulation of expression and physicobiochemical properties. Fungal degradation of methyleneureas may occur via the formation of organic acids, thus leading to a nonenzymatic degradation of methyleneureas, which are unstable under acidic conditions.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Antonie van Leeuwenhoek 62 (1992), S. 173-179 
    ISSN: 1572-9699
    Keywords: activity ; Pseudomonas aeruginosa ; regulation ; urea uptake ; urease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The energy-dependent urea permease was studied in two strains ofPseudomonas aeruginosa, measuring the uptake (transport and metabolism) of14C-urea. In both strains urea uptakein vivo and urease activityin vitro differed significantly with respect to kinetic parameters, temperature and pH dependence and response to metabolic inhibitors. Ammonium strongly interfered both with the expression of the urea uptake system and its activity. The inhibition of the uptake activity by ammonium was partially relieved by hydraziniumsulfate, which prevented the translocation of ammonium into the cell, and in a methylammonium/ammonium transport-defective mutant of strain DSM 50071. Furthermore, methionine-sulfoximine, which prevented the intracellular glutamine formation from ammoniumvia inhibition of glutamine synthetase, relieved the inhibition of urea uptake by ammonium. These findings suggested that urea uptake activity inP. aeruginosa is regulated by intracellular glutamine.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 145 (1986), S. 306-310 
    ISSN: 1432-072X
    Keywords: Ammonium uptake ; Methylammonium ; Nitrogen control ; Cold shock ; Alcaligenes eutrophus H16
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The uptake of the radioactive ammoniumanalogue 14C-methylammonium1 was measured in heterotrophically grown cells of Alcaligenes eutrophus H16 in order to study the mechanism of NH 4 + uptake. MA gradients of up to 200 were built up by a substrate-specific and energy-dependent system which showed a K m of 35–111 μM and a V max of 0.4–1.8 nmol MA/min per mg protein. The involved carrier exhibited a higher affinity towards NH 4 + than towards CH3NH 3 + indicating that ammonium rather than MA was its natural substrate. Cold shock with hypotonic but not with hypertonic solutions caused the efflux of almost the entire accumulated MA. Osmotic shock did not affect the uptake reaction, suggesting that no periplasmic binding proteins were involved. Indirect observations indicate the membrane potential as driving force for MA uptake. High rates of uptake were observed in cells grown under nitrogen deficiency or with nitrate as nitrogen source. The uptake rate decreased during growth at high ammonium concentrations indicating that biosynthesis of nitrogenous compounds was supported by passive diffusion of NH3. The data suggest that the formation of the carrier is subject to “nitrogen control”.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-072X
    Keywords: Sporosarcina ureae ; NAD ; glutamate dehydrogenase ; Heat-stability ; Cold-lability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract NAD-specific glutamate dehydrogenase (NAD-GluDH; EC 1.4.1.2) was purified to homogeneity from Sporosarcina ureae DSM 320; the native enzyme (M r 250,000±25,000) is composed of subunits identical in molecular mass (M r 42,000±3,000), suggesting a hexameric structure. In cell-free extracts and in its purified form, the enzyme was heat-stable, retaining 50% activity after 15 min incubation at temperatures up to 82°C. When exposed to low temperatures at pH values between 7.0 and 9.0. cell-free extracts and purified preparations lost enzyme activity rapidly and irreversibly. The addition of substrates, glycerol, or sodium chloride improved the stability of the enzyme with respect to cold lability and heat stability.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 165 (1996), S. 265-271 
    ISSN: 1432-072X
    Keywords: Key wordsBacillus pasteurii ; Leucine transport ; Ammonium stimulation ; Sodium-dependence ; Leucine transport dehydrogenase ; Abbreviations CCCp carbonylcyanide-m-chlorphenylhydrazone ; DCCD N,N'-Dicyclohexylcarbodiimide ; LeuDH Leucine dehydrgenase ; ΔΨ Membrane potential ; ΔpH pH gradient; Δp, Proton motive force
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The kinetics, specificity and mechanism of leucine uptake were studied in the alkaliphilic bacterium Bacillus pasteurii DSM 33 (ATCC 11859). Leucine was accumulated up to 200-fold by a sodium-dependent secondary transport system for branched-chain amino acids. Apparent Kt values of 9.6 μM for leucine, 8.9 μM for isoleucine, 9.3 μM for valine, and 0.71 mM for sodium were determined, and maximum uptake activity was observed at an external pH of 8.5 and at 35°C. The effect of several ionophores indicated that transport was energized by the membrane potential and a sodium gradient; each gradient alone was sufficient to drive the uptake of leucine. The activity of the leucine transport system was regulated by the intracellular pH and was inhibited at an internal pH below 7.0.
    Type of Medium: Electronic Resource
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