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  • 1
    Electronic Resource
    Electronic Resource
    Occurrence and significance of nitrogen transport in the brown alga Laminaria digitata (1983)
    Springer
    Marine biology 77 (1983), S. 107-112 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen transport in a Laminaria digitata (Huds.) Lamour population growing at Arbroath, Scotland has been investigated (during the period 3 June 1981 to 3 July 1981), using 15N as tracer. NO 3 - was assimilated both by the blade meristem and by the mature blade. NO 3 - uptake by the blade meristem alone was insufficient to supply the nitrogen demand for growth. This additional demand was met by nitrogen transport from the mature blade to the meristem. It was estimated that 70% of the nitrogen demand of the meristematic region was supplied by nitrogen transport from the mature blade. Although transport occurred, the size of the endogenous pool of stored nitrogen in the mature blade did not change, the quantity of nitrogen transported being equivalent to the amount of NO 3 - assimilated during the experimental period. The possible co-transport of nitrogen and carbon is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00396307
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  • 2
    Electronic Resource
    Electronic Resource
    Osmotic adjustment and organic solute accumulation in unicellular cyanobacteria from freshwater and marine habitats (1985)
    Springer
    Marine biology 88 (1985), S. 1-9 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The intracellular concentrations of low-molecular weight carbohydrates and quaternary ammonium compounds present in 26 axenic isolates of unicellular cyanobacteria have been studied over a range of external salinity from freshwater up to 300% seawater (100%=35‰ S). In all cases, a single carbohydrate, either sucrose or glucosylglycerol, was identified as the principal organic osmoticum, showing major variation in response to the external salt concentration; quaternary ammonium compounds were present in osmotically insignificant amounts. Glucosylglycerol was accumulated as primary osmoticum by nine of the isolates from saline habitats and by five of the freshwater isolates; trace amounts of sucrose were also prsent. The remaining twelve freshwater strains accumulated sucrose as sole osmoticum. Glucosylglycerol-accumulating strains grew over the widest salinity range (up to 200 to 250% seawater), whether isolated from saline or non-saline habitats. Sucrose-accumulating strains were more stenohaline, growing only in up to 50 to 100% seawater and showing no sustained growth in hypersaline media (〉100% seawater). The data suggest that (1) glycosylglycerol accumulation is not unique to marine cyanobacteria, and (2) the upper salinity limit for growth may be linked to organic solute accumulation, rather than habitat, with glucosylglycerol-accumulating isolates having a greater potential for growth in salt-stressed conditions than sucrose accumulators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393037
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  • 3
    Electronic Resource
    Electronic Resource
    Physiological responses of Nodularia harveyana to osmotic stress (1984)
    Springer
    Marine biology 79 (1984), S. 21-26 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of salinity stress on biomass yield, photosynthetic O2 evolution and nitrogenase activity were investigated using axenic cultures of Nodularia harveyana (Thwaites) Thuret originally isolated from a salt marsh at Gibraltar Point, Lincolnshire, UK in 1971 and studied in this laboratory in 1983. Biomass yields, as chlorophyll a per culture, were highest in the 0 to 100% seawater (0 to 35‰ sea salt) range with negligible growth in 200% seawater; growth on NH 4 + was greater than on N2 and NO 3 - , which did not differ significantly from each other. In short-term experiments, photosynthetic O2 evolution remained high at salinities up to 150% seawater (52.5‰ sea salt); nitrogenase activity remained high at salinities up to 100% seawater (35‰ sea salt). The major internal low molecular weight carbohydrate which accumulated in response to increased salinity was sucrose, the levels of which fluctuated markedly and rapidly in response to salinity change.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00404981
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  • 4
    Electronic Resource
    Electronic Resource
    Organic solute accumulation in osmotically-stressed Enteromorpha intestinalis (1987)
    Springer
    Marine biology 95 (1987), S. 583-592 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of organic solutes in the osmotic adjustment processes of the marine macroalga Enteromorpha intestinalis (L.) Link was investigated in 1986, using fresh samples collected from mid-shore rock pools at Tayport, Fife, Scotland. Natural-abundance 13C nuclear magnetic-resonance spectroscopy revealed β-dimethylsulphoniopropionate (DMSP) to be the only major low molecular weight organic osmolyte present. However, on transfer to a hypersaline medium (300% sea water; 100%=35 S‰), tissue sucrose and proline levels increased markedly, while DMSP remained constant. Recovery of optimal photosynthetic activity and increases in inorganic ion levels occurred over a similar time scale to the changes in sucrose and proline (within 48 h), indicating that these two organic solutes are involved in hyperosmotic adjustment in E. intestinalis while DMSP is not. Freshly-collected plants transferred to 300% sea water medium in the dark showed no significant increases in organic osmolytes. In contrast, starch-enrichment (16 d continuous illumination) led to enhanced synthesis of sucrose and proline in the light and in darkness, but tissue DMSP levels showed no variation throughout. These observations suggest that DMSP is not involved in short-term osmoacclimation in E. intestinalis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393102
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  • 5
    Electronic Resource
    Electronic Resource
    The incorporation of nitrogen into products of recent photosynthesis in Anabaena cylindrica Lemm. (1976)
    Springer
    Archives of microbiology 107 (1976), S. 15-24 
    Details
    ISSN: 1432-072X
    Keywords: Blue-green algae ; Nitrogen metabolism ; Intermediary carbon metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In vivo tracer studies with 14C have been performed to help determine pathways of incorporation of newly assimilated nitrogen into N2-fixing cells of Anabaena cylindrica. After photosynthesis in Ar:O2:14CO2 for 30 min, the addition of N2 or NH 4 + resulted in increased rates of 14CO2-incorporation both in the light and dark, and in increased incorporation of 14C into amino acids at the expense of sucrose and sugar phosphates. Evidence of enhanced sucrose catabolism and increased pyruvate kinase activity was obtained on adding nitrogen, and, of the 14C-labelling entering the tricarboxylic acid cycle, more appeared in citrate and 2-oxoglutarate than in malate and oxaloacetate. The kinetics of 14C-incorporation into various amino acids suggest that in the light and dark the most important route of primary ammonia assimilation involves glutamine synthetase and that glutamate, aspartate, glycine and probably alanine are formed secondarily from glutamine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00427862
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  • 6
    Electronic Resource
    Electronic Resource
    Alanine dehydrogenase of the N2-fixing blue-green alga, Anabaena cylindrica (1976)
    Springer
    Archives of microbiology 107 (1976), S. 115-124 
    Details
    ISSN: 1432-072X
    Keywords: Alanine dehydrogenase ; Anabaena cylindrica ; Heterocysts ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The l-alanine dehydrogenase (ADH) of Anabaena cylindrica has been purified 700-fold. It has a molecular weight of approximately 270000, has 6 sub-units, each of molecular weight approximately 43000, and shows activity both in the aminating and deaminating directions. The enzyme is NADH/NAD+ specific and oxaloacetate can partially substitute for pyruvate. The K m app for NAD+ is 14 μM and 60 μM at low and high NAD+ concentrations, respectively. The K m app for l-alanine is 0.4 mM, that for pyruvate is 0.11 mM, and that for oxaloacetate is 3.0 mM. The K m app for NH 4 + varies from 8–133 mM depending on the pH, being lowest at high pH levels (pH 8.7 or above). Alanine, serine and glycine inhibit ADH activity in the aminating direction. The enzyme is active both in heterocysts and vegetative cells and activity is higher in nitrogen-starved cultures than in N2-fixing cultures. The data suggest that although alanine is formed by the aminating activity of ADH, entry of newly fixed ammonia into organic combination does not occur primarily via ADH in N2-fixing cultures of A. cylindrica. Ammonia assimilation via ADH may be important in cultures with an excess of available nitrogen. The deaminating activity of the enzyme may be important under conditions of nitrogen-deficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00446830
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  • 7
    Electronic Resource
    Electronic Resource
    Nitrogenase activity in extracts of heterocystous and non-heterocystous blue-green algae (1970)
    Springer
    Archives of microbiology 74 (1970), S. 235-243 
    Details
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cell-free extracts capable of acetylene reduction and cyanide reduction have been prepared from heterocystous (Anabaena cylindrica) and non-heterocystous (Plectonema boryanum 594) blue-green algae. Extracts from Anabaena were obtained from cultures grown in blulk under aerobic conditions, while the Plectonema cultures were grown in bulk on nitrate-nitrogen, then washed free from nitrate and sparged with A/CO2 for 40 h after which time maximum nitrogenase activity was detected. The nitrogenases of both algae are similar and resemble in many respects nitrogenases from bacteria and legumes. Activity is located primarily in a 40,000xgx15 min supernatant fraction and the rate of C2H2 reduction observed is about 10 per cent of whole cell activity. ATP and a source of reducing power (Na2S2O4) are required for efficient functioning of the enzyme. ATP-dependent hydrogen evolution occurs, the extracts are cold labile and highly sensitive to oxygen and the oxygen inhibition is irreversible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00408884
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  • 8
    Electronic Resource
    Electronic Resource
    d-Ribulose 1,5-diphosphate carboxylase from the blue-green alga Aphanocapsa 6308 (1977)
    Springer
    Archives of microbiology 113 (1977), S. 105-110 
    Details
    ISSN: 1432-072X
    Keywords: d-Ribulose 1,5-diphosphate carboxylase ; Quaternary structure ; Oxygenase activity ; Aphanocapsa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract d-Ribulose 1,5-diphosphate carboxylase from extracts of the unicellular blue-green alga Aphanocapsa 6308 has been purified by ammonium sulphate precipitation and linear sucrose density gradient centrifugation. The molecular weight was estimated to be 525 000 and the enzyme consisted of two types of sub-unit of molecular weights 51 000 and 15 000. The small sub-units were not detected after purification involving acid precipitation but were observed if the acid precipitation step was omitted. The Michaelis constants for Mg2+ and CO2, when tested under air, were 0.35 mM and 0.071 mM respectively. Oxygen acted as a competitive inhibitor with respect to CO2, suggesting that the enzyme also acts as an oxygenase. This was confirmed by measuring ribulose diphosphate-dependent O2 uptake. A 1:1 stoichiometry between ribulose diphosphate utilization and O2 consumption was observed. 6-Phosphogluconate inhibited carboxylase activity both at high (20 mM) and low (1 mM) bicarbonate concentrations. The data are compared with the properties of ribulose diphosphate carboxylase from other autotrophic prokaryotes and from chloroplasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00428589
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  • 9
    Electronic Resource
    Electronic Resource
    Alteration of cyanobacterial glutamine synthetase activity in vivo in response to light and NH 4 + (1979)
    Springer
    Archives of microbiology 120 (1979), S. 195-200 
    Details
    ISSN: 1432-072X
    Keywords: Blue-green algae ; Cyanobacteria ; Glutamine synthetase ; Light-modulation ; Anabaena cylindrica ; NH 4 + -deactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Extractable glutamine synthetase activity of the cyanobacterium Anabaena cylindrica was reduced by approximately 50% when N2-fixing cultures were treated with 10 mM NH 4 + or were placed in darkness. The deactivated enzyme could be rapidly reactivated (within 5 min) by adding 40 mM 2-mercaptoethanol to the biosynthetic reaction mixture. The enzyme could also be reactivated in vivo by replacing the culture in light or by removing NH 4 + . When the enzyme was deactivated by simultaneously adding NH 4 + and placing the culture in darkness, reactivation occurred on reillumination and removal of NH 4 + . The removal of NH 4 + in darkness did not result in reactivation. On in vitro reactivation of glutamine synthetase from dark or NH 4 + -treated cultures the maximum glutamine synthetase activity observed frequently exceeded that of glutamine synthetase extracted from untreated cultures. Anacystis nidulans showed a similar type of reversible dark deactivation to A. cylindrica but Plectonema boryanum and a Nostoc did not. With A. cylindrica, a direct positive correlation between the size of the intracellular pool of glutamate and biosynthetic glutamine synthetase activity occurred during light/dark shifts, and on treatment with NH 4 + . The changes in activity of glutamine synthetase in A. cylindrica in response to light resemble in some respects the light modulation of enzymes of the oxidative and reductive pentose phosphate pathways noted in cyanobacteria by others.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00423065
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  • 10
    Electronic Resource
    Electronic Resource
    Osmotic adjustment in cyanobacteria from hypersaline environments (1984)
    Springer
    Archives of microbiology 138 (1984), S. 333-337 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Osmotic adjustment ; Osmoregulation ; Quaternary ammonium compounds ; Glycine betaine ; Halotolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The intracellular concentrations of the monovalent inorganic cations K+ and Na+, low molecular weight carbohydrates and quaternary ammonium compounds have been determined for 4 strains of cyanobacteria (Aphanothece halophytica, Coccochloris elabens, Dactylococcopsis salina and Synechocystis DUN52) originally isolated from hypersaline habitats (i.e. habitats with a salinity greater than that of seawater) over a range of external salt concentration (from 50% to 400% seawater). Intracellular cation levels (Na+ and K+) were determined to be within the range 80–320 mmol · dm-3 (cell volume), showing only minor changes in response to salinity. Intracellular carbohydrates were found to comprise a negligible component of the intracellular osmotic potential [at 2–19 mmol · dm-3 (cell volume)], throughout the salinity range. Quaternary ammonium compounds, however, were recorded in osmotically significant quantities [up to 1,640 mmol · dm-3 (cell volume)] in these strains, showing major variation in response to salinity. Thus Synechocystis DUN 52 showed an increase in quaternary ammonium compounds in the oder of 1,200 mmol · dm-3 between 50% and 400% seawater medium, accounting for a significant proportion of the change in external osmotic potential. Examination of intact cells and cell extracts using 13C and 1H nuclear magnetic resonance (NMR) spectroscopy confirmed the presence of the quaternary ammonium compound glycine betaine as the major osmoticum in the 4 strains; no other compounds were detected during NMR assays. These results suggest a common mechanism of osmotic adjustment, involving quaternary ammonium compounds, in cyanobacteria from hypersaline environments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00410900
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