Ammonia Uptake in the Alkalophilic Cyanobacterium Spirulina platensis

Ammonia uptake was studied in the alkalophilic cyanobacteriumSpirulina platensis. In continuous cultures under optimal growthconditions ammonia supported optimal growth (doubling time of9.3 h), causing a reduction of glutamine synthetase activityto 25% of that found in cultures grown on NO₃. Long term (20min) ammonia uptake assays were performed to study the dependencyon metabolism: 1) Ammonia uptake proceeded at the same ratesin the light and in the dark, the pH dependency pattern correlatingwith light-dependent O₂ evolution and dark O₂ consumption. 2)The uptake of ammonia was pH dependent with an optimum at pH9.3. 3) The uptake was totally dependent upon the activity ofglutamine synthetase and was completely inhibited by methoininesulfoximine. To study the mechanism by which NH₄⁺/NH₃ enters the cells, shortterm experiments (up to 1 min) were performed at pH 7.0 andpH 10.0: At pH 7.0 the uptake was slow and at a constant rate.At pH 10.0, the uptake did not saturate even at 1 mM ammoniaand the kinetics were biphasic, consisting of a fast componentlasting less than 5 seconds and of a subsequent slower component.The fast phase was insensitive to methionine sulfoximine, whereasthe slower phase was completely inhibited by this compound.We suggest that under optimal (alkaline) pH the entry of ammoniainto Spirulina cells is likely to be a pH driven diffusion process,continuously supported by its intracellular assimilation. ¹Contribution number 35 of the Microalgal Biotechnology Laboratory. (Received September 19, 1988; Accepted January 16, 1989)     

Thermal characteristics of Spirulina platensis cells under nongrowing conditions at various values of pH medium

The total value of heat (-Q) evolved by green-blue microalgae Spirulina platensis cells in a dark and stationary regime in the range of pH values 8.0-11.6 was determined. It was established that (-Q) reaches its maximum value at 360 +/- 40 J/g of dry biomass in the pH range 9.3-10.3 and then sharply dropped relative to these values and reached zero at pH 7.5 +/- 0.2 and 11.8 +/- 0.2. It is affirmed that an optimum regime for preservation of Spirulina platensis cell viability in a dark and stationary regime is pH range 9.3-10.3. It was also shown that the peak of heat evolution with maximum about 45 degrees C, reflecting mainly the respiration of cells (oxygen absorption rate), did not displace along the temperature scale at a change of pH from 9.3 to 10.4 and slightly displaced lower and higher of these values of pH. It is supposed that the thermostability of biomacromolecules and their complexes responsible for cell respiration does not depend on pH medium in pH range 9.3-10.3.     

Action of Spirulina platensis on bacterial viruses

The impact of the biomass of the blue-green microalga (cyanobacterium) S. platensis on bacteriophage T4 (bacterial virus) has been evaluated. The study revealed that the addition of S. platensis biomass into the agar nutrient medium, followed by sterilization with 2% chloroform and thermal treatment, produced an inhibiting or stimulating effect on the reproduction of the bacteriophage in Escherichia coli B cells, depending on the concentration of S. platensis and the multiplicity of phage infection, as well as on the fact whether the microalgae were added during the first cycle of the development of the virus. The reproduction of the bacteriophage in E. coli B was influenced by the method and duration of the sterilization of the nutrient medium with S. platensis.     

Resistance to Azetidine-2-carboxylic Acid and Sodium Chloride Tolerance in Carrot Cell Cultures and Spirulina platensis

Mutants of Spirulina platensis and of Daucus carota resistantto azetidine-2-carboxylic acid were tested for NaCl tolerance.A positive correlation was found between proline overproductionand osmotolerance. In carrot lines proline overproduction wasnot strictly proportional to NaCl tolerance insofar as cellscharacterized by differences in proline overproduction showedsimilar osmotolerance, suggesting that other factors could beinvolved. (Received March 17, 1983; Accepted June 14, 1983)     

基于蛋白质组学对螺旋藻砷胁迫响应机制的研究

通过研究螺旋藻(Spirulina sp.)在砷离子胁迫下的蛋白质组变化,从蛋白质表达水平解释螺旋藻对砷离子胁迫的响应机理。螺旋藻经过不同浓度砷离子胁迫7 d后,提取蛋白质进行凝胶电泳,并对差异蛋白进行质谱分析。结果表明螺旋藻在2.0 ppm砷酸盐中暴露10 min光合放氧速率降低27.3%,培养24 h后细胞内的金属硫蛋白、叶绿素、类胡萝卜素及藻胆蛋白相对含量均明显降低。蛋白组学共鉴定出75个差异蛋白,其中26个显著上调,49个呈现下调。这些差异蛋白表明砷离子主要通过破坏螺旋藻光合色素蛋白,干扰电子传递过程,导致能量合成受损,使得依赖光合作用产生能量进行的跨膜运动、蛋白质合成等相关过程受到影响;同时,活性氧清除与防御相关蛋白呈现上调,螺旋藻细胞内抗氧化系统被激活。     

Accumulation of poly-beta-hydroxybutyrate in Spirulina platensis.

Poly-beta-hydroxybutyrate has been identified in the cyanobacterium Spirulina platensis. The addition of reduced carbon compounds to the growth medium was not required for poly-beta-hydroxybutyrate accumulation. Poly-beta-hydroxybutyrate accumulated during exponential growth to 6% of the total dry weight and then decreased during the stationary phase.     

Biosequestering Potential of Spirulina platensis for Uranium

The uranium sequestering potential of Spirulina platensis was studied in batch mode, and its equilibrium was established in approximately 60 minutes. It had maximum sorption at pH 4.0 to 4.5. Equilibrium data is well represented by the Langmuir isotherm model followed by the Freundlich and Redlich-Peterson models. The interference of other cations and anions in solution was found to decrease sorption of the uranium, suggesting a competition for sorption sites on S. platensis. The desorption results showed that sodium citrate solution is effective, with 83% of uranium being recovered through nondestructive means.     

Alginate immobilization of Spirulina platensis for wastewater treatment

Immobilization of cyanobacterium Spirulina platensis in sodium alginate (1.5 %) gave the best quality of bead and 15-16 beads were formed per mL of aqueous solution of alginate. The immobilized cells were used in a batch process for treatment of diluted sewage. After 8 days, 95 % of BOD5, 77 % of COD, 90 % of ammonia, and 94 % of TSS were removed.     

Carbonic anhydrase of blue-green alga Spirulina platensis]

Carboanhydrase (carbonate-hydroliase EC 4.2.1.1.) is found in the extract of Spirulina platensis cells. A linear dependency of the enzyme activity on the protein concentration; pH optimum is found to be 8.0. Specific activity of carboanhydrase is 3 muM/min-mg of protein under the concentration of CO2 of 4-10(-3) M, appearing Michelis constant being 4.9-10(-3) M. The enzyme was stabilized with 10 mM of cisteine, its activity was inhibited by 50% with sulphanylamide (1-10(-5) M), acetazolamide (8--10(-7) M) and Cl- ions (5-10(-2) M). The activity of carboanhydrase, as well as the rate of NaH14CO3 fixation, depended on the pH value of cultural medium.     

Raceway cultivation of Spirulina platensis using underground water

The semi-outdoor cultivation of Spirulina platensis was attempted using an underground-water-based medium. Occurrence of contaminant organisms such as Chlorella sp. and Chlamydomonas sp. was not found from a microscopic observation and bacteria were not detected from denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rDNA during the cultivation, owing to pH control and the high quality of the underground water. The mean productivity was high at 10.5 g/m2/d with a range of 4.2-12.3 g/m2/d despite the unfavorable weather conditions of the rainy season. The cultivated S. platensis included a normal protein content of 58.9%. Consequently, the underground water improved the biomass productivity and the biomass quality because of an abundant supplementation of natural minerals and through a contaminant-free culture.     

The response of the filamentous cyanobacterium Spirulina platensis to salt stress

The responses of the filamentous cyanobacterium Spirulina platensis to increased NaCl concentrations (0.25–1.0 M) in addition to the concentration of sodium in the growth medium were studied. A two stage response to the salt stress was observed. This consisted of a relatively short shock stage, followed by adaptation process. It was shown that upon exposure to high salt concentrations of 0.5 M and above, immediate inhibition of photosynthesis and respiration, and complete cessation of growth occurred. After a time lag, the energy-yielding processes exhibited restored activity. At 0.5 and 1.0M NaCl photosynthesis reached 80% and 50% that of the control, while respiration was enhanced by 140 and 200%, respectively. The time lags were longer when the cells were exposed to higher NaCl concentrations. The resumption of growth and the establishment of new steady state growth rates were found to be correlated to the recovery in respiration. The relationship between the growth rates after adaptation and the increased NaCl concentrations was found to be inversely linear. The cellular sodium content was maintained at a constant low level, regardless of the external NaCl concentration, while potassium content declined linearly vs. the external NaCl concentration. The carbohydrate content of the cells rose exponentially with the increase in NaCl concentration.Publication No. 34 from the Micro-Algal Biotechnology Lab.     

Growth of Spirulina platensis enhanced under intermittent illumination

The growth characteristics of microalgae under different light conditions (continuous or intermittent) are essential information for photobioreactor design and operation. In this study, we constructed a thin-layer (10 mm) flat plate photobioreactor device with a light/dark (L/D) alternation system to investigate the growth of Spirulina platensis under two different light regimes: (1) continuous illumination in a wide range of light intensities (1.00-77.16 mW cm⁻²); (2) intermittent illumination in medium frequency (0.01-20 Hz). Specific growth rate and light efficiency based on biomass production were determined for each round of experiment. Four regions (light limited region, intermediate region, light saturated region and light inhibition region) were recognized according to the results under continuous illumination. Under intermittent illumination, when L/D frequency increased from 0.01 Hz to 20 Hz, specific growth rate and light efficiency were enhanced. However, the enhancement was different, depending on the applied light intensity and light fraction. The higher the light intensity, the greater the enhancement would be when L/D frequency increased from 0.01 Hz to 20 Hz; and the higher the light intensity, the lower the light fractions is needed to maintain light efficiency as high as that under continuous illumination in light limited region.     

Antioxidant activities of phycocyanobilin prepared from Spirulina platensis

The antioxidative activity of phycocyanobilin fromSpirulina platensis was evaluated againstoxidation of methyl linoleate in a hydrophobic systemor with phosphatidylcholine liposomes. Phycocyanobilin as well as phytochemicals including-tocopherol, caffeic acid and zeaxanthin,effectively inhibited the peroxidation of methyllinoleate and produced a prolonged induction period.Oxidation of phosphatidylcholine liposomes was alsocontrolled markedly by adding phycocyanobilin or-tocopherol. Phycocyanobilin was distributedoutside in the liposomes to scavenge radicals fromAAPH and to prevent initiation of radical chainreactions. When the concentrations of phycocyanin andphycocyanobilin in the reaction mixture were adjustedequally on a phycocyanobilin basis, the activity ofphycocyanobilin was almost the same as that ofphycocyanin in the AAPH-containing reaction mixture.The antioxidizing action of phycocyanin prepared fromspray-dried Spirulina almost agreed with thatfrom fresh Spirulina in the AAPH-containingreaction mixture. These results suggest thatphycocyanobilin is responsible for the majority of theantioxidative activity of phycocyanin and may act asan effective antioxidant in a living human body.     

钝顶螺旋藻富集转化硒及硒在藻体中的分布

钝顶螺旋藻在４℃、避光、隔离空气条件下,对硒的吸附量死体显著高于活体。藻体对硒的最大富集量为６２７．４μg.g^-1(DW),培养基中硒浓度在３００μg.ml^-1以下时有机硒转化率大于８０％。藻体中的硒主要分布在水溶性组化率大于８０％。藻体中的硒主要分布在水溶性组分中,占总硒的６５％以上,蛋白质硒占有机硒的７１．９％,多糖、核酸也有一定量硒分布。     

Photosynthetic characterization of a mutant of Spirulina platensis

A mutant of Spirulina(Arthrospira) platensis, strain I22,obtained by mutagenesis with ethylmethanesulfonate, was partially defective inthe production of -linolenic acid. However, when compared with the wildform, the I22 mutant almost lost its capacity to grow at low temperatures,although at optimal temperature growth was unaffected. Measurement of themutant's photosynthetic characteristics, including O₂-evolution,Pmaxand light saturation values, revealed significantly lower values than for thewild type, in contrast to the higher content of photosynthetic pigments,chlorophyll and phycocyanin. Whereas the total activity of photosynthesis oftheI22 mutant was 58% lower than that of the wild type, the PS II activity of theI22 mutant was 23% higher. On the other hand, the I22 mutant was 69% lower inPSI activity, and the growth rate of this mutant was limited at high lightintensity. These results indicated that the defect in the PS I complex of theI22 mutant may reduce its ability to utilize light to generate the energy usedin diverse biochemical processes, including fatty acid desaturation.     

Photooxidative damage to the cyanobacterium Spirulina platensis mediated by singlet oxygen

Experiments on the specific growth rate, bleaching of pigments, O₂ evolution, lipid peroxidation, and loss of sulfhydryl (-SH) content in response to the varying light intensities (2–28 W/m²) suggested that photodamage to the Spirulina cells was maximum at or beyond the photosynthesis saturating light intensity (12 W/m²). However, photobleaching of the chlorophyll a was relatively higher than carotenoid. The results on the N,N-dimethyl-p-nitrosoaniline (RNO) bleaching in the presence of oxygen radical quenchers exhibited maximum effect of sodium azide and indicated about the generation of singlet oxygen. The chlorophyll a-sensitized production of singlet oxygen by a type II reaction cannot be ruled out because of maximum oxidative damage to the cells at or beyond the photosynthesis saturating light intensity, i.e., 12 W/m², when the availability of triplet chlorophyll is maximum.