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  • 1
    Electronic Resource
    Electronic Resource
    Osmotic adjustment in Spirulina platensis (1985)
    Springer
    Planta 163 (1985), S. 424-429 
    Details
    ISSN: 1432-2048
    Keywords: Cyanobacteria ; Glucosyl-glycerol ; Osmotic adjustment ; Spirulina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The filamentous cyanobacterium Spirulina platensis has been examined for salt tolerance and osmotic adjustment. Salinities up to 150% seawater had little effect on growth yield or photosynthetic O2 evolution; higher salinities were markedly inhibitory. Osmotic adjustment was achieved by the intracellular accumulation of the low-molecular-weight carbohydrate glucosyl-glycerol in response to increased external salinity: in fullstrength (100%) seawater glucosyl-glycerol accounted for approximately 5.0% of the dry weight of the cyanobacterium. Trehalose was also present, particularly in cells at low salt concentration, and in 50% seawater medium accounted for up to 1.0% of the dry weight of the cyanobacterium. For cells grown in 100% seawater the ratio of trehalose to glucosyl-glycerol varied with temperature: at 37°C trehalose comprised 31% (w/w) of the low-molecular-weight carbohydrates while at 20°C only 9% of the total was trehalose. When subjected to hypo-osmotic shock the intracellular concentration of glucosyl-glycerol decreased and this was mirrored by an increase in glycogen. An understanding of the osmotic adjustment of S. platensis has implications both for the mass culturing of this and other strains of Spirulina and possibly also for the quality of the harvested product.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395153
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  • 2
    Electronic Resource
    Electronic Resource
    A glycine betaine transport system in Aphanothece halophytica and other glycine betaine-synthesising cyanobacteria (1987)
    Springer
    Archives of microbiology 147 (1987), S. 399-405 
    Details
    ISSN: 1432-072X
    Keywords: Aphanothece halophytica ; Cyanobacteria ; Glycine betaine ; Halotolerance ; Osmotic stress ; Transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Uptake of exogenous 14C-glycine betaine has been followed in the cyanobacterium Aphanothece halophytica and other species able to synthesise glycine betaine in response to osmotic stress. At 1 mmol dm−3 uptake was rapid (flux rate=29.50 nmol m−2 s−1), equilibrating at an internal concentration of 120 mmol dm−3 within 30 min. This rapid uptake, coupled with high internal accumulation, was characteristic of glycine betaine-synthesising cyanobacteria only. The 14C-glycine betaine transported was not catabolised. Kinetic studies indicated a Michaelis-Menten type relationship (K m=2.0 μmol dm−3, V max=45 nmol min−1 mm−3 cell volume), with a pH optimum of 8.0–8.5. Darkness dramatically decreased the flux rate. Higher 14C-glycine betaine levels occurred in cells growth in medium of elevated osmotic strength, and glycine betaine uptake was sensitive to changes in external salinity. A relationship between Na+ availability and glycine betaine uptake was observed, with 〉80 mmol dm−3 Na+ required for optimal stimulation of uptake in seawater-grown cells. Severe hyperosmotic stress (1000 mmol dm−3 NaCl) reduced the rate of glycine betaine uptake but increased internal glycine betaine concentration at equilibrium. Hypo-osmotic stress caused a decline in the internal glycine betaine concentration due to an increased rate of loss, indicating that the efflux system was also sensitive to ambient salinity changes. It is envisaged that this active transport system may be an adaptive mechanism in halophilic glycine betaine-synthesising cyanobacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00406140
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Changes in turgor pressure in response to increases in external NaCl concentration in the gas-vacuolate cyanobacterium Microcystis sp. (1985)
    Springer
    Archives of microbiology 143 (1985), S. 290-296 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Turgor pressure ; Salt shock ; Turgor regulation ; K+ uptake, Microcystis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in cell turgor pressure have been followed in cells of Microcystis sp. transferred to culture medium containing added NaCl at osmolalities of 30–1,500 mosmol kg-1 (≡ 74–3,680 kPa). Upon upshock turgor decreased, due to osmotically-induced water loss from the cell. However, partial recovery of turgor was then observed in illuminated cells, with maximum turgor regain in media containing 30–500 mosmol kg-1 NaCl. The lightdependent recovery of turgor pressure was completed within 60 min, with no evidence of further changes in cell turgor up to 24 h. This is the first direct evidence that turgor regulation may occur in a prokaryotic organism. Short-term increases in cell K+ content were also observed upon upshock in NaCl, indicating that turgor regain may involve a turgorsensitive K+ uptake system. Estimation of internal K+ concentration in cells transferred to 250 mosmol kg-1 NaCl showed that changes in cell K+ may account for at least half of the observed turgor regain up to 60 min.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00411252
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  • 5
    Electronic Resource
    Electronic Resource
    Blue-green algae (cyanobacteria): prospects and perspectives (1985)
    Springer
    Plant and soil 89 (1985), S. 97-106 
    Details
    ISSN: 1573-5036
    Keywords: Blue-green algae ; Cyanobacteria ; Osmotic responses ; Salinity tolerance ; Spirulina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Photosynthetic, prokaryotic blue-green algae (cyanobacteria) occur in a wide range of natural habitats of diverse ionic composition and as such, represent an important source of biological material for biosolar energy conversion programs using saline water. The gasvacuolate, filamentous Spirulina is grown in ‘seminatural’ culture in Lake Texcoco, Mexico, as a major source of single-cell protein for animal nutrition. Pilot-scale trials in other areas of the world have also demonstrated the suitability of blue-green algae, including Spirulina, for growth under brackish conditions. The carbohydrate accumulation profiles of blue-green algae differ in isolates from freshwater, marine and hypersaline habitats, with a trend towards sucrose or trehalose accumulation in stenohaline freshwater strains grown in media containing NaCl, while euryhaline and marine forms frequently accumulate glucosylglycerol. Many halotolerant isolates from hypersaline habitats accumulate glycinebetaine in response to osmotic stress. This knowledge may provide scope for future improvement in the N2 fixation rates of blue-green algae in saline media, using betaine-accumulating N2-fixing strains in preference to other, saltsensitive isolates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02182236
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