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  • 1
    Electronic Resource
    Electronic Resource
    Osmotic responses of unicellular blue-green algae (cyanobacteria): changes in cell volume and intracellular solute levels in response to hyperosmotic treatment (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 9 (1986), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Changes in cell volume and solute content upon hyperosmotic shock have been studied for six unicellular blue-green algae (cyanobacteria): Synechococcus PCC 6301, PCC 6311; Synechocystis PCC 6702, PCC 6714, PCC 6803 and PCC 7008. The extent of change in volume was shown to be dependent upon the solute used to establish the osmotic gradient, with cells in NaCl showing a reduced shrinkage when compared to cells in media containing added sorbitol and sucrose. Uptake of extracellular solutes during hyperosmotic shock was observed in Synechocystis PCC 6714, with maximum accumulation of external solutes in NaCl and minimum solute uptake in sucrose solutions. Conversely, solute loss from the cells (K+ and amino acids) was greatest in sucrose-containing media and least in NaCl. The results show that these blue-green algae do not behave as ‘ideal osmometers’ in media of high osmotic strength. It is proposed that short-term changes in plasmalemma permeability in these organisms may be due to transient membrane instability resulting from osmotic imbalance between the cell and its surrounding fluid at the onset of hyperosmotic shock.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11612699
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  • 2
    Electronic Resource
    Electronic Resource
    The compatibility of osmotica in cyanobacteria (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 11 (1988), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. The solutes accumulated by cyanobacteria in response to hyper-osmotic stress include Na+, K+, sucrose, trehalose, glucosyl-glycerol, glyeine betaine and glutamate betaine. The compatibility of several of these solutes with glutamine synthetase activity has been examined using cell-free extracts from a range of freshwater, marine and halotolerant cyanobacteria. All of the solutes tested were compatible with (i.e. non-inhibitory to) enzymic activity at physiological concentrations and the results demonstrate a rank order of compatibility which correlates with the concentrations at which the organic solutes occur in cyanobacteria, i.e. glycine betaine 〉 polyol-derivatives 〉 disaccharides and with the upper salinity limit for growth. The protection against inhibition by NaCl (halo-protection) afforded by these solutes to enzymic activity was also examined. Only glycine betaine was found to exert a significant halo-protective effect and this may be explained by differences in the mechanism of compatible solute function between small charged molecules and sugars/polyols.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11604910
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  • 3
    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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  • 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
    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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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Osmoacclimation in Enteromorpha intestinalis: long-term effects of osmotic stress on organic solute accumulation (1988)
    Springer
    Marine biology 98 (1988), S. 467-476 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of salinity variation on organic solute accumulation have been studied in marine Enteromorpha intestinalis (L.) Link (St. Andrews, Fife, National Grid Ref. NO 514168, and Fife Ness, Fife, National Grid Ref. NO 638098) collected from upper mid-shore rock pools from January to July 1987; and in freshwater E. intestinalis (Forfar Loch, Angus, National Grid Ref. NO 440504) collected during August 1986, in short-term (48 h) and long-term (35 d) experiments. The tertiary sulphonium compound β-dimethylsulphoniopropionate (DMSP) was the principal organic osmolyte in unstressed cells; marine plants contained greater amounts of DMSP than freshwater plants. Exposure to increased salinity resulted in the short-term accumulation of proline and sucrose, while DMSP was unchanged in freshwater and marine plants. In longer-term exposure to salt stress, sucrose levels declined while DMSP increased and proline levels remained high. Long-term incubation in hypersaline media increased the tissue protein and chlorophyll levels of marine E. intestinalis; this may be linked to changes in the cytoplasm:vacuole ratio of the cell. Prolonged exposure to hyposaline and hypersaline conditions led to changes in DMSP content in the manner predicted for an osmotic effector, suggesting that DMSP is involved in long-term osmoacclimation in Enteromorpha spp. The results are also consistent with the proposal that DMSP acts as a compatible cytosolute in Enteromorpha species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391537
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  • 9
    Electronic Resource
    Electronic Resource
    Method for determination of turgor pressure in macroalgae, with particular reference to the Phaeophyta (1988)
    Springer
    Marine biology 99 (1988), S. 473-480 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A procedure is described for the determination of the internal osmotic pressure and turgor pressure of marine macroalgae, for use in the laboratory and on the shore. A volume-related parameter (either thallus fresh weight, or area) is measured before and after transfer of plant material to a range of hyperosmotic solutions. Plotting the final fresh weight/area as a percentage of the initial value gives a biphasic curve, with an initial component of negative slope due to the change in thallus volume in less extreme hyperosmotic solutions, where the non-rigid thallus contracts in response to decreasing cell turgor pressure. The second component has a shallower slope and represents plasmolysis in more extreme hyperosmotic solutions, i.e., where turgor pressure is reduced to zero and the protoplast shrinks away from the cell wall; the extraprotoplast space created by plasmolysis will be filled with the external solution and thus no further changes in weight occur. These two components intersect at the lowest osmotic pressure at which cell turgor is zero. By correcting for any effects of the cell wall on thallus volume, the relationship can be used to calculate internal osmotic pressure and hence turgor pressure, assuming that the remaining change in thallus volume of the initial component is due entirely to variation in the intraprotoplast volume (approximately equivalent to the intraprotoplast water content, determined by subtraction of the extraprotoplast water and dry weight from the thallus fresh weight). Using this procedure, the turgor pressures of Fucus spiralis L., Ectocarpus siliculosus, (Dillw.) Lyngb. and Laminaria digitata (Huds.) Lamour. (from Fife Ness, Scotland, May–August 1987) in a seawater-based medium were 0.82, 0.58 and 1.34 Osmol kg−1, respectively. The turgor pressure of F. spiralis on the shore at Fife Ness (June 1987) was 0.74 Osmol kg−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392554
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  • 10
    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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