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  • 1
    Electronic Resource
    Electronic Resource
    Modification of NO−3 metabolism in heterocysts of the N2-fixing cyanobacterium Anabaena 7120 (ATCC27893) (1986)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 36 (1986), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The utilization of NO−3, NO−2 and NH+4 was studied in whole filaments and isolated heterocysts of Anabaena 7120 (ATCC27893). NO−3- and NO−2-uptake were detectable in whole filaments but not in heterocysts, whereas NH+4-uptake was detectable in both. Activity of NO−3-reductase was present in cell-free extracts of whole filaments but not of heterocysts, whereas activities of NO−2-reductase and glutamine synthetase were present in both. NO−3-uptake and reductase activities could not be induced in heterocysts even after prolonged incubation in NO−3 medium. It is suggested that NO−3-metabolism in heterocysts is impaired due to a selective and irreversible loss of NO−3-uptake and reductase systems resulting in the abolition of competition for molybdenum cofactor (Mo-Co) and reductant between nitrogenase and NO−3-reductase, and an increase in glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1986.tb01682.x
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  • 2
    Electronic Resource
    Electronic Resource
    Nitrogenase in free-living and symbiotic cyanobacteria: Immunoelectron microscopic localization (1986)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 35 (1986), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Nitrogenase (Fe-protein) was localized in the free-living cyanobacterium Anabaena cylindrica and in the cyanobionts of Cycas revoluta and Peltigera aphthosa, using colloidal gold as an immunocytochemical marker. The Fe-protein was found to be evenly distributed throughout the heterocyst cytoplasma in A. cylindrica and in both the cyanobionts, including multiple heterocysts of the C. revoluta cyanobiont. No label was observed in the vegetative cells of free-living A. cylindrica or of the cyanobionts, although the cyanobionts apparently live under microaerobic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1986.tb01502.x
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  • 3
    Electronic Resource
    Electronic Resource
    Correlation between nitrogenase and glutamine synthetase expression in the cyanobacterium Anabaena cylindrical (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 80 (1990), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Distribution pattern and levels of nitrogenase (EC 1.7.99.2) and glutamine synthetase (GS, EC 6.3.1.2) were studied in N2-, NO3− and NH4+ grown Anabaena cylindrica (CCAP 1403/2a) using immunogold electron microscopy. In N2- and NO3− grown cultures, heterocysts were formed and nitrogenase activity was present. The nitrogenase antigen appeared within the heterocysts only and showed an even distribution. The level of nitrogenase protein in the heterocysts was identical with both nitrogen sources. In NO3− grown cells the 30% reduction in the nitrogenase activity was due to a corresponding decrease in the heterocyst frequency and not to a repressed nitrogenase synthesis. In NH4− grown cells, the nitrogenase activity was almost zero and new heterocysts were formed to a very low extent. The heterocysts found showed practically no nitrogenase protein throughout the cytoplasm, although some label occurred at the periphery of the heterocyst. This demonstrates that heterocyst differentiation and nitrogenase expression are not necessarily correlated and that while NH4+ caused repression of both heterocyst and nitrogenase synthesis, NO3− caused inhibition of heterocyst differentiation only. The glutamine synthetase protein label was found throughout the vegetative cells and the heterocysts of all three cultures. The relative level of the GS antigen varied in the heterocysts depending on the nitrogen source, whereas the GS level was similar in all vegetative cells. In N2- and NO3+ grown cells, where nitrogenase was expressed, the GS level was ca 100% higher in the heterocysts compared to vegetative cells. In NH4+ grown cells, where nitrogenase was repressed, the GS level was similar in the two cell types. The enhanced level of GS expressed in heterocysts of N2 and NO3− grown cultures apparently is related to nitrogenase expression and has a role in assimilation of N2derived ammonia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1990.tb04368.x
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  • 4
    Electronic Resource
    Electronic Resource
    Nitrate metabolism in the cyanobacterium Anabaena cycadeae: Regulation of nitrate uptake and reductase by ammonia (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 63 (1985), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Nitrogen regulation of nitrate uptake and nitrate reductase (EC 1.7.99.4) was studied in the cyanobacterium Anabaena cycadeae Reinke and its glutamine auxotroph. Development of the nitrate uptake system preceded, and was independent of, the development of the nitrate reductase system. The levels of both systems were several-fold higher in the glutamine auxotroph lacking glutamine synthetase (EC 6.3.1.2) than in the wild type strain having normal glutamine synthetase activity. The nitrate uptake system was found to be NH4-repressible and the nitrate reductase system NO3−-inducible. NH4+ was the initial repressor signal for the uptake process which was involved in the control of the NO3−inducible reductase system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1985.tb04273.x
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  • 5
    Electronic Resource
    Electronic Resource
    Mycobiont-cyanobiont interactions during dark nitrogen fixation by the lichen Peltigera aphthosa (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 57 (1983), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Acetylene reduction (nitrogenase activity) by excised cephalodia of Peltigera aphthosa Willd. slowly declined on transfer of the cephalodia from light to darkness. The decline was more rapid in the absence of CO2 or when phosphoenolpyruvate carboxylase activity was inhibited by adding maleic acid or malonic acid. When glutamine synthetase (GS) activity was totally inhibited by adding l-methionine-dl-sulphoximine (MSX) the decline in nitrogenase activity in the absence of CO2 still occurred. However, this loss of activity did not occur when the mycobiont was disrupted using digitonin (0.01 % w/v) and the fixed NH4+ was released into the medium. The data suggest that dark CO2 fixation by the fungus supplies carbon skeletons which remove newly fixed NH4+ produced by the cyanobacterium. When such carbon skeletons are not available MH4+ accumulates and inhibits nitrogenase activity even in the absence of GS activity. It is probable that NH4+ and a product of GS exert independent inhibitory effects on nitrogenase activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1983.tb00912.x
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  • 6
    Electronic Resource
    Electronic Resource
    Glycolate metabolism in cyanobacteria (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 75 (1989), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The mechanism for uptake of glycolate in the cyanobacterium Anabaena 7120 and its capacity to metabolize glycolate were examined. The uptake of [14C]-glycolate in light, at pH 7, consisted of an initial rapid phase (≤60s) and a second slower phase. The latter obviously represents metabolism as the glycolate dehydrogenase inhibitor 2-pyridylhydroxymethanesulfonic acid (HPMS) did not affect the initial uptake phase while the second phase was strongly reduced. The sulfhydryl reagent N-ethylmaleimide (NEM) inhibited uptake of glycolate and the uptake was reduced by lactate, glycerate and glyoxylate, Treatment with triphenylmethylphosphonium (TPMP+), a lipophilic cation collapsing ΔΨ only slightly reduced the uptake of glycolate. At pH 7.0, the F0F1-ATPase inhibitor N, N′-dicyclohexylcarbodiimide (DCCD) and the uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP) abolished the uptake. Inhibition of photophosphorylation by dark-treatment and presence of 3-(3′,4′-dichlorophenyl)-1, 1-dimethylurea (DCMU) also reduced the uptake. Decreasing the pH in the range of 10 to 5.5 increased the uptake. In contrast to the situation at pH 7. CCCP did not affect the initial glycolate uptake at pH 5.5. We conclude that the uptake of glycolate is a carrier-mediated process which, at pH 7, is dependent on a H+-ATPase to create the ΔpH across the membranes needed for uptake, while at pH 5.5 the uptake of glycolate is not ATP-dependent. The capacity to metabolize glycolate was at least 50 μmol (mg chl a)−1 h−1 in young cultures. In older cultures the rate was nearly 50% lower.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1989.tb06161.x
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  • 7
    Electronic Resource
    Electronic Resource
    Interactions between cyanobacterium and fungus during 15N2-incorporation and metabolism in the lichen Peltigera canina (1983)
    Springer
    Archives of microbiology 134 (1983), S. 136-142 
    Details
    ISSN: 1432-072X
    Keywords: Ammonia assimilation ; Lichen symbioses ; Nitrogen fixation ; 15N kinetics ; Peltigera canina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract On following N2-incorporation and subsequent metabolism in the lichen Peltigera canina using 15N as tracer, it was found, over a 30 min period, that greatest initial labelling was into NH 4 + followed by glutamate and the amide-N of glutamine. Labelling of the amino-N of glutamine, aspartate and alanine increased slowly. Pulse-chase experiments using 15N confirmed this pattern. On inhibiting the GS-GOGAT pathway using l-methionine-dl-sulphoximine and azaserine, 15N enrichment of glutamate, alanine and aspartate continued although labelling of glutamine was undetectable. From this and enzymic data, NH 4 + assimilation in the P. canina thallus appears to proceed via GS-GOGAT in the cyanobacterium and via GDH in the fungus; aminotransferases were present in both partners. The cyanobacterium assimilated 44% of the 15N2 fixed; the remainder was liberated almost exclusively as NH 4 + and then assimilated by fungal GDH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00407946
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  • 8
    Electronic Resource
    Electronic Resource
    Evidence for an ammonium transport system in free-living and symbiotic cyanobacteria (1984)
    Springer
    Archives of microbiology 137 (1984), S. 241-246 
    Details
    ISSN: 1432-072X
    Keywords: Ammonium transport ; Anabaena azollae ; Anabaena variabilis ; Cyanobacteria ; Methylammonium transport ; Symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The free-living cyanobacterium Anabaena variabilis showed a biphasic pattern of 14CH3NH 3 + uptake. Initial accumulation (up to 60 s) was independent of CH3NH 3 + metabolism, but long-term uptake was dependent on its metabolism via glutamine synthetase (GS). The CH3NH 3 + was converted into methylglutamine which was not further metabolised. The addition of l-methionine-dl-sulphoximine (MSX), to inhibit GS, inhibited CH3NH 3 + metabolism, but did not affect the CH3NH 3 + transport system. NH 4 + , when added after the addition of 14CH3NH 3 + , caused the efflux of free CH3NH 3 + ; when added before 14CH3NH 3 + , NH 4 + inhibited its uptake indicating that both NH 4 + and CH3NH 3 + share a common transport system. Carbonylcyanide m-chlorophenylhydrazone and triphenyl-methylphosphonium both inhibited CH3NH 3 + accumulation indicating that the transport system was Δψ-dependent. At pH 7 and at an external CH3NH 3 + concentration of 30 μmol dm-3, A. variabilis showed a 40-fold intracellular accumulation of CH3NH 3 + (internal concentration 1.4 mmol dm-3). Packets of the symbiotic cyanobacterium Anabaena azollae, directly isolated from the water fern Azolla caroliniana, also showed a Δψ-dependent NH 4 + transport system suggesting that the reduced inhibitory effect of NH 4 + on nitrogenase cannot be attributed to the absence of an NH 4 + transport system but is probably related to the reduced GS activity of the cyanobiont.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00414551
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  • 9
    Electronic Resource
    Electronic Resource
    Evidence for a common genetic regulation of glutamine synthetase and nitrate uptake and reductase in the cyanobacterium Anabaena cycadeae (1985)
    Springer
    Molecular genetics and genomics 198 (1985), S. 367-368 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nitrate uptake and reductase activities of the cyanobacterium Anabaena cycadeae and its mutant, lacking glutamine synthetase, (the glutamine auxotroph) were measured. The levels of both these enzymes were up to 25-fold higher in the mutant than in the parent (Anabaena cycadeae). the data indicate operation of a common genetic regulatory mechanism controlling the loss of the primary ammonia assimilating enzyme, glutamine synthetase, and derepression of the nitrate uptake and reductase systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00383023
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  • 10
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    Interactions between cyanobacterium and fungus during 15N2-incorporation and metabolism in the lichen Peltigera canina (1983)
    Springer
    Details
    Publication Date: 1983-02-01
    Print ISSN: 0302-8933
    Electronic ISSN: 1432-072X
    Topics: Biology
    Published by Springer
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