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  • 2020-2023
  • 1995-1999  (2)
  • Cyanobacterium  (1)
  • Nitrate reductase  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Effects of increased atmospheric CO2 and N supply on photosynthesis, growth and cell composition of the cyanobacterium Spirulina platensis (Arthrospira) (1998)
    Springer
    Journal of applied phycology 10 (1998), S. 461-469 
    Details
    ISSN: 1573-5176
    Keywords: Cyanobacterium ; Spirulina platensis ; Arthrospira ; CO2 ; organic carbon ; nitrogen ; photosynthesis ; batch culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The consequences of the addition of CO2 (1%) in cultures of S. platensis are examined in terms of biomass yield, cell composition and external medium composition. CO2 enrichment was tested under nitrogen saturating and nitrogen limiting conditions. Increasing CO2 levels did not cause any change in maximum growth rate while it decreased maximum biomass yield. Protein and pigments were decreased and carbohydrate increased by high CO2, but the capability to store carbohydrates was saturated. C:N ratio remained unchanged while organic carbon released to the external medium was enhanced, suggesting that organic carbon release in S. platensis is an efficient mechanism for the maintenance of the metabolic integrity, balancing the cell C:N ratio in response to environmental CO2 changes. CO2 affected the pigment content: Phycocyanin, chlorophyll and carotenoids were reduced in around 50%, but the photosynthetic parameters were slightly changed. We propose that in S. platensis CO2 could act promoting degradation of pigments synthetised in excess in normal CO2 conditions, that are not necessary for light harvesting. Nitrogen assimilation was significantly not affected by CO2, and it is proposed that the inability to stimulate N assimilation by CO2 enrichment determined the lack of response in maximum growth rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008090402847
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Optimized nitrate reductase assay predicts the rate of nitrate utilization in the halotolerant microalga Dunaliella viridis (1997)
    Springer
    Journal of applied phycology 9 (1997), S. 99-106 
    Details
    ISSN: 1573-5176
    Keywords: Nitrate reductase ; in situ enzymatic activity ; Dunaliella viridis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An in situ method for measuring nitrate reductase (NR) activity in Dunaliella viridis was optimized in terms of incubation time, concentration of KNO3, permeabilisers (1-propanol and toluene), pH, salinity, and reducing power (glucose and NADH). NR activity was measured by following nitrite production and was best assayed with 50 mM KNO3, 1.2 mM NADH, 5% 1-propanol (v/v), at pH 8.5. The estimated half-saturation constant (Ks) for KNO3 was 5 mM. Glucose had no effect as external reducing power source, and NADH concentrations 〉1.2 mM inhibited NR activity. Nitrite production was linear up to 20 min; longer incubation did not lead to higher nitrate reduction. The use of the optimized assay predicted the rate of NO 3 − removal from the external medium by D. viridis with high degree of precision.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007978512458
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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