Jasmonic acid affects changes in the growth and some components content in alga Chlorella vulgaris

The present study was undertaken to test the influence of exogenous applied jasmonic acid upon the growth and changes in some metabolites levels in the cells of green alga Chlorella vulgaris Beijerinck (Chlorophyceae). It was found, that JA in algal cells acted in a concentration-dependent manner. Treatment with JA at high concentrations range of 10⁻⁵–10⁻⁴ M, resulted in the decrease in cell number and reduction of major photosynthetic pigments, monosaccharides, soluble cellular and extracellular proteins levels as well as decrease in pH of the medium. In contrast to 10⁻⁵ and 10⁻⁴ M JA, this phytohormone applied at 10⁻⁸–10⁻⁶ M induced the increase in cell number, photosynthetic pigments and monosaccharides contents, significant accumulation and extracellular secretion of soluble proteins over control and neutralization of the medium. Quantitative changes in polypeptide pattern of total cellular proteins after treatment with the optimal concentration of 10⁻⁷ M JA on the 7^th day of cultivation as analyzed by SDS-PAGE, was also observed. JA induced synthesis de novo of 15 specific polypeptides with molecular weight 334-16 kDa which were’t detected in the control. The data suggest that JA plays a important role in algal growth and development.     

Studies on the incorporation of CO2 into starch by Chlorella vulgaris

Chlorella vulgaris was grown photosynthetically in batch culture under nitrogen sufficiency or nitrogen limitation. The starch content of the cells was measured as the amount of glucose released by enzymic hydrolysis of partially purified starch. Nitrogen sufficient algae contained approximately 20% of their dry weight as starch, whereas in nitrogen limited cells starch comprised up to 55% of the cellular dry weight. Starch production was pH dependent; optimal production of starch was achieved between pH 7.5 and 8.0. Optimal growth of C. vulgaris occurred at pH 7.0. Carbon yield experiments showed that for every gram of carbon consumed 0.5 g of starch (glucose) could be recovered. author for correspondence     

Effect of oxygen on the growth (yield) of Chlorella vulgaris

The growth yield of Chlorella vulgaris, Y _kJ defined as g cells harvested per kJ of light energy absorbed by the cells, was assessed in a turbidostat culture by varying CO₂ and O₂ partial pressures ( and ). The value of Y _kJ ranged from 3.1×10^-3 to 5.0×10^-3 g cells/kJ under light-limited conditions [ = 1.02.4%, = 065%; total pressure of gas (composed of CO₂, O₂ and N₂)=1 atm]. In the light-limited environment, the algal specific growth rate deteriorated appreciably with the increase of . The deterioration accounts for the above range of Y _kJ observed. The growth inhibition due to oxygen that was defined by subtracting from 1.0 the ratio of at given values of to that at = 0% extended from 0.07–0.30 (7–30%). However, glycolate could not be detected in the turbidostat culture. Isotopic experiments on the specific rate of ¹⁴CO₂ uptake also revealed that the inhibition due to oxygen was from 22–38% when was varied from 0 to nearly 100%. These effects of oxygen were discussed, referring to the activity of ribulose-1,5-bisphosphate carboxylase that is inhibited competitively by oxygen.Non-Standard Abbreviations INH isonicotinic acid hydrazide - PPO 2,5-diphenyloxazole - DCMU 3-(-3,4-dichlorophenyl)-1,1-dimetylurea - CA carbonic anhydrase - RuP₂ ribulose-1,5-bisphosphate     

Deoxyribonucleic acid reassociation in the taxonomy of the genus Chlorella

Four species of the unicellular green alga Chlorella, C. vulgaris, C. luteoviridis, C. minutissima, and C. zofingiensis, were characterized with respect to DNA similarities as determined by quantitative DNA hybridization procedures. In contrast to previous DNA hybridization procedures. In contrast to previous results, C. vulgaris turned out to be a homogeneous species with the exception of strain 211-11c of the Göttingen collection, which was shown to belong to C. kessleri. Similary, C. luteoviridis and C. minutissima represent well defined species in terms of phenotypic and genotypic features. Whitin C. zofingiensis on strain is clearly different with respect to DNA base composition and DNA hybridization data even though it shares phenotypic characteristics with the other strains of C. zofingiensis.     

Gold uptake by Chlorella vulgaris

This paper describes a study on the uptake of gold (III) ions by viable and treated cells of the unicellular alga, Chlorella vulgaris. Inactivating the algal cells by various physical/chemical treatments resulted in a considerable enhancement in the uptake capacity over the pristine cells. X-ray Photoelectron Spectroscopy (XPS) analyses confirmed the deposition of elemental gold, Au (O), on the cell surface, indicating that a reduction process has taken place. XPS results also suggested an increase in the oxidized carbon species, carboxyl species in particular, on the surfaces of the treated cells. FTIR spectroscopy results revealed that the carboxyl group was involved mainly in the binding of the gold on the surface of both the viable and treated cells.     

The effect of biochanin A on the chlorophylls and carotenoids content in the alga <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> Beijerinck

The present study was undertaken to determine the influence of biochanin A, isoflavone characterised by estrogenic activity, upon the content of chlorophylls and carotenoids in the cells of green alga Chlorella vulgaris Beijerinck (Chlorophyceae). On the 6^th day of cultivation under the influence of 10⁻⁶ M biochanin A exerted the greatest biological activity and the most stimulating effect on the analysed parameters: growth of the alga expressed by the cells number and the content of photosynthetic pigments in them. The total content of carotenoids was stimulated on the 6^th day of experiment in the range of 197 % but during the 9^th day only in 179 % in comparision with the control group (100 %). At the same time content of carotenes increased to the level of 123 – 119 % and xanthophylls to 208 – 178 %. Among the carotenes, β-carotene was characterised with the 3.7 times higher content in regard to the content of α-carotene on the 6^th day of cultivation and during the 9^th day — the 5.7 times domination. The content of xanthophylls that contain two atoms of oxygene in molecule (oxygen — poor xanthophylls) was intensively stimulated in the range of 224 %. Moreover, the oxygen — rich xanthophylls content reached the value 179 % when compared to the control. The greatest stimulation of the content of chlorophylls and its isomers was observed during the 3^rd day of cultivation of Chlorella vulgaris when it rose up to 166 % and to 156 % on the 6^th day. The content of chlorophyll b and its isomers was stimulated in 181 % on the 6^th day of culture and 155 % during the 9^th day of algal culture. The evidence on the stimulating effect of biochanin A as the main representative of isoflavones on the growth and content photosynthetic pigments in eucaryotic alga C. vulgaris was demonstrated in these studies.     

Effect of high nitrate concentrations on growth and nitrate uptake by free-living and immobilizedChlorella vulgaris cells

Growth and nitrate uptake were studied on free-living and immobilizedChlorella vulgaris cells cultivated in medium containing different nitrate concentrations. First, the effect of nitrate concentrations on growth indicated that cells can live in the presence of high concentrations as high as 97 mM. Although no lethal effect on cells was observed such concentration a slow down in growth and a decrease in biomass produced was observed. The rate of nitrate uptake increased with the nitrate concentration in the medium. The maximum uptake rate was reached in first days of culture in both free-living and immobilized cells. The rate dropped more rapidly for cells growing in 2 mM nitrate than for cells growing in higher nitrate concentration. The maximum rate was very much the same for free-living and immobilized and was within the order of 0.45 to 0.57 g NO₃ h^–1 10^–6 cells. Immobilization modified the changes of nitrate uptake rate for concentration higher than 2 mM.     

Harvesting of Chlorella vulgaris using a bioflocculant from Paenibacillus sp. AM49

Microbial flocculants for harvesting mass cultured Chlorella vulgaris were screened and that from Paenibacillussp. AM49 was identified as the best. The flocculation efficiency of this bioflocculant increased with the pH within a range of pH 5–11 and was 83%, which was higher than the 72% and 78% produced by aluminum sulfate and polyacrylamide, respectively. The highest flocculation efficiency was with 6.8 mm CaCl₂ as co-flocculant. The bioflocculant from Paenibacillussp. AM49 can be used effectively to harvest C. vulgaris from large-scale cultures.     

Cycloheximide induces synchronous swelling of perialgal vacuoles enclosing symbiotic Chlorella vulgaris and digestion of the algae in the ciliate Paramecium bursaria

Cycloheximide is known to inhibit preferentially protein synthesis of symbiotic Chlorella of the ciliate Paramecium bursaria, but to hardly host protein synthesis. Treatment of algae-bearing Paramecium cells with cycloheximide induces synchronous swelling of all perialgal vacuoles that are localized immediately beneath the host's cell membrane. In this study, the space between the symbiotic algal cell wall and the perialgal vacuole membrane widened to about 25 times its normal width 24 h after treatment with cycloheximide. Then, the vacuoles detached from beneath the host's cell membrane, were condensed and stained with Gomori's solution, and the algae in the vacuoles were digested. Although this phenomenon is induced only under a fluorescent light condition, and not under a constant dark condition, this phenomenon was not induced in paramecia treated with cycloheximide in the light in the presence of the photosynthesis inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea. These results indicate that algal proteins synthesized in the presence of algal photosynthesis serve some important function to prevent expansion of the perialgal vacuole and to maintain the ability of the perialgal vacuole membrane to protect itself from host lysosomal fusion.     

Effects of phenolic compounds on growth and metabolic activities of Chlorella vulgaris and Scenedesmus bijugatus isolated from soil

Phenol and three nitrophenols (o-nitrophenol, m-nitrophenol, p-nitrophenol), commonly occurring pollutants in natural eco-systems, were tested for their toxic effects on soil isolates of Chlorella vulgaris and Scenedesmus bijugatus, growing under phototrophic, photoheterotrophic and heterotrophic conditions. The toxicity criteria included cell number, chlorophyll, total protein and carbohydrate content, ¹⁴CO₂ uptake and in vivo nitrate reductase activity. Both C. vulgaris and S. bijugatus were sensitive to the pollutants when the cultures were grown under phototrophic or heterotrophic conditions. However, the toxicity was found reversed or alleviated upon photoheterotrophic growth of the cultures. Transmission electron microscope studies revealed various cytological abnormalities in C. vulgaris in the presence of phenolics at algistatic levels.     

Biotechnological potential of Chlorella vulgaris for accumulation of Cu and Ni from single and binary metal solutions

This study provides information on the mechanism(s) of Cu and Ni ion biosorption by C. vulgaris, distinguishing adsorption from intracellular accumulation under various conditions. Surface adsorption was found to contribute maximally (>70%) to total Cu/Ni ion accumulation by the test alga (total accumulation efficiencies were 60 and 53 g metal ion mg protein^–1, respectively for Cu and Ni). Maximum intracellular uptake was reported at a pH range of 6.5–7.5, whereas adsorption reached its maximum at pH 3.5 for Cu, and pH 3.5 and 6.5 in the case of Ni. 35 °C was found to be the best temperature for maximum adsorption, whereas intracellular uptake was highest at 25 °C. Though exponentially grown C. vulgaris registered maximum metal ion uptake, adsorption maxima reached the highest values in the declining phase of the culture. Heat-killed and air-dried C. vulgaris accumulated Cu and Ni at about 80% of the values for viable samples, whereas formaldehyde-treated and immobilized biomasses depicted better accumulating potential than the control cells. Na, K, Mn and Zn caused competitive inhibition, whereas for Ca a mixed-type inhibition was evident. Thus, the present study suggests that the general concept that cations inhibit metal ion accumulation by competing with them for the same binding sites on the cell surface is not absolutely valid. As these results also demonstrate that a large amount of the bound metal (>70%) is in the adsorbed fraction, it is advantageous in the sense that it could be recovered by a suitable desorbing agent, especially in case of precious metals and the biomass could be exploited for repeated use in reactors.     

Inhibition of Chlorella growth by the lipids of cyanobacterium Microcystis aeruginosa

The total lipids of the cyanobacterium Microcystis aeruginosa have been isolated and fractionated into its components. Of these lipid components, only the fatty acid-containing fraction inhibited the growth of the green alga Chlorella pyrenoidosa. The inhibitory activity appears to be due to linoleic and linolenic acids, which are both present in significants quantities. These acids may be the substances responsible for the reported toxicity of Microcystis aeruginosa to Chlorella.     

Enhanced Chlorella vulgaris Buitenzorg growth by photon flux density alteration in serial photobioreactors

Microalgae perform oxygenic photosynthesis and are capable of taking up a large amount of CO₂, using an inducible CO₂ concentrating mechanism (CCM), and fixing CO₂ into higher compounds. These characteristics make the microalgae potentially useful for removal and utilization of CO₂ emitted from industrial plants and, generally, the usage of photosynthetic microorganisms has increased and significantly improved as a solution for CO₂ emissions. In this light and based on previous research using Anabaena cylindrica IAM M1 and Spirulina platensis IAM M 135, enhancement was sought for CO₂ fixation and biomass production by Chlorella vulgaris Buitenzorg by increasing the photon flux density concurrent with increases in culture biomass during the cellular growth phase and was compared to cultures of Chlorella grown at optimal constant illumination, with all cultures grown using Bennick basal medium, 29°C, and a flow of 1.0 atm. 10% CO₂ enriched air delivered to three in serial photobioreactors of 0.200 dm³ capacity each. The results showed that increasing illumination during culture increased biomass production of Chlorella by ∼60% as well as increased CO₂ fixation ability by ∼7.0%. It was also demonstrated that the non-competitive inhibition of [HCO₃ ⁻] as a carbon source significantly affected the cultivation in both the increasing and constant photon flux density regimes.     

Isolation and characterization of brassinosteroids from algal cultures of Chlorella vulgaris Beijerinck (Trebouxiophyceae)

The brassinosteroids (BRs) occur ubiquitously in the plant kingdom. The occurrence of BRs has been demonstrated in almost every part of higher plants, such as pollen, flower buds, fruits, seeds, vascular cambium, leaves, shoots and roots. In this study, BRs were isolated and identified in the culture of wild-type Chlorella vulgaris. Seven BRs, including teasterone, typhasterol, 6-deoxoteasterone, 6-deoxotyphasterol, 6-deoxocastasterone, castasterone and brassinolide, were identified by GC–MS. All compounds belong to the BR biosynthetic pathway. The results suggest that early and late C6 oxidation pathways are operating in C. vulgaris. This study represents the first isolation of BRs from C. vulgaris cultures.     

Mechanistic characterization of omega-3 desaturation in the green alga Chlorella vulgaris

alpha-Linolenic acid (ALA, 9(Z),12(Z),15(Z)-octadecatrienoic acid) derivatives are important plant lipids which play a critical key role in cold tolerance. The final steps of ALA biosynthesis feature a series of regio- and stereoselective dehydrogenation reactions which are catalyzed by a set of enzymes known as fatty acid desaturases. In conjunction with ongoing research into the structural biology of these remarkable catalysts, we have examined the mechanism of double bond introduction at C15,16 as it occurs in a model photosynthetic organism, Chlorella vulgaris. The individual deuterium kinetic isotope effects associated with the C-H bond cleavages at C-15 and C-16 of a thialinoleoyl analogue were measured via competition experiments using appropriately deuterium-labelled 7-thia substrates. A large kinetic isotope effect (KIE) (k(H)/k(D)=10.2+/-2.8) was observed for the C-H bond-breaking step at C-15 while the C-H bond cleavage at C-16 was found to be relatively insensitive to deuterium substitution (k(H)/k(D)=0.8+/-0.2). These results point to C-15 as the site of initial oxidation in omega-3 desaturation and imply that the Chlorella and corresponding plant systems share a common active site architecture.     

Metal resistance and removal by two strains of the green alga, <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> Beijerinck,isolated from Laguna de Bay,Philippines

Two strains of Chlorella vulgaris Beijerinck isolated from two different sites in Laguna de Bay, Philippines, were studied for their resistance and ability to remove four metal ions, i.e., Cu²⁺, Cr⁶⁺, Pb²⁺, and Cd²⁺ added separately in BG-11 growth medium. The growth of the two strains was severely inhibited at 2 mg.L⁻¹ of Cu²⁺, 5 mg.L⁻¹ of Cr⁶⁺, 8 mg.L⁻¹ of Pb²⁺, and 10 mg.L⁻¹ of Cd²⁺. However, the two strains exhibited different EC₅₀ values for the same metal ion. The WB strain had a significantly higher resistance (p < 0.01) for Cd²⁺ and Cr⁶⁺ compared with the SB strain, while the SB strain had significantly higher resistance (p < 0.01) for Cu²⁺ compared with the WB strain. On the other hand, the two strains behaved differently in their capacity to remove the metal ions in BG-11 medium containing 1.0 mg.L⁻¹ of the three metal ions, except for Cu²⁺, which was added at 0.1 mg.L⁻¹. The WB strain showed the highest removal of Cd²⁺ at 70.3% of total, followed by Pb²⁺ at 32%, while the SB strain exhibited the highest removal of Pb²⁺ at 48.7% followed by Cd²⁺ at 40.7% of the total. Both strains showed the least removal of Cr⁶⁺ at 28% and 20.8% of the total for the WB and SB strains respectively. The percentage removal for Cu²⁺ was 50.7% and 60.8% for the WB and SB strains respectively. After 12 days of incubation, both strains showed that a greater percentage of the metal ions removed were accumulated intracellularly than adsorbed at a ratio of at least 2:1. Both strains manifested the same cytological deformities, like a loss of pyrenoids at 10 mg.L⁻¹ in all four metal ions. Discoloration and disintegration of chloroplasts were observed at 1.0 mg.L⁻¹ in Cu²⁺ and 5 mg.L⁻¹ in Cr⁶⁺. The nonrelease of autospores from the mother cells was observed at 10 mg.L⁻¹ in Cu²⁺ and Cr⁶⁺. Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines.     

Deoxyribonucleic acid reassociation in the taxonomy of the genus Chlorella

DNA hybridization techniques showed Chlorella fusca var. vacuolata and C. kessleri to be homogeneous species with DNA homologies of 90–100% C. fusca var. fusca and var. rubescens, however, have only about 15% DNA homology with C. fusca var. vacuolata and should no longer be regarded as varieties. A good correlation was found so far between biochemical and physiological characters used in the taxonomy of Chlorella and DNA relatedness. Mutant strains of Chlorella were tested for DNA homologies to prove the reliability of the taxonomical interpretation.     

Photoconversion of long-wavelength protochlorophyll native form Pchl 682/672 into chlorophyll Chl 715/696 in Chlorella vulgaris B-15

By spectral methods, the final stages of chlorophyll formation from protochlorophyll (ide) were studied in heterotrophic cells of Chlorella vulgaris B-15 mutant, where chlorophyll dark biosynthesis is inhibited. It was shown that during the dark cultivation, in the mutant cells, in addition to the well-known protochlorophyll (ide) forms Pchlide 655/650, Pchl(ide) 640/635, Pchl(ide) 633/627, a long-wavelength protochlorophyll form is accumulated with fluorescence maximum at 682 nm and absorption maximum at 672 nm (Pchl 682/672). According to the spectra measured in vivo and in vitro, illumination of dark grown cells leads to the photoconversion of Pchl 682/672 into the stable long wavelength chlorophyll native form Chl 715/696. This reaction was accompanied by well-known photoreactions of shorter-wavelength Pchl (ide) forms: Pchlide 655/650Chlide 695/684 and Pchl (ide) 640/635Chl (ide) 680/670. These three photoreactions were observed at room temperature as well as at low temperature (203–233 K).Abbreviations Chl chlorophyll - Chlide chlorophyllide - Pchlide protochlorophyllide - Pchl protochlorophyll - PS I RC Photosystem I reaction centres. Abbreviations for native pigment forms: the first number after the pigment symbol corresponds to maximum position of low-temperature (77 K) fluorescence band (nm), second number to maximum position of long-wavelength absorption band     

Influence of culture density,pH, organic acids and divalent cations on the removal of nutrients and metals by immobilized Anabaena doliolum and Chlorella vulgaris

The potential of alginate-immobilized Anabaena doliolum and Chlorella vulgaris was assessed for removal of nutrients (NO _inf3 ^sup- and NH _inf4 ^sup+ ) and metals (Cr₂O _inf7 ^sup2- and Ni²⁺) at different biomass concentrations (0.05, 0.1, 0.25, 0.49 and 1.22 g dry wt l^-1) and pH values (4 to 10). Though uptake of all these substances was higher in concentrated algal beads (0.25, 0.49 and 1.22 g dry wt l^-1), their rate of uptake was significantly (P<0.001) lower than that of low (0.05 g dry wt l^-1) cell density beads. For A. doliolum, there was no significant difference in uptake rates for beads having densities of 0.05 and 0.1 g dry wt l^-1. Chlorella vulgaris, however, showed maximum efficiency at 0.1 g dry wt l^-1. Uptake of both the nutrients and the metals was maximal at pH 7 followed by pH 8, 6, 9, 10, 5 and 4. Of the different substances (organic acids and divalent cations) used, humic acid was most efficient in decreasing metal uptake. Mg²⁺ was, however, more efficient than Ca²⁺ in decreasing Ni²⁺ uptake. Immobilized algae with a cell density of 0.1 g dry wt l^-1 were the most efficient for nutrient and metal removal at pH 6 to 8.     

Hexose-transport-deficient mutants of Chlorella vulgaris

Autotrophically grown cells of Chlorella vulgaris show a strong increase in the uptake rates for hexoses and for seven amino acids when incubated in the presence of hexoses. This increase is due to de-novo synthesis of three transport proteins: one forhexoses and two for amino acids. Mutants deficient in hexose transport were obtained after treatment of wild-type cells with acridine orange, followed by a selection procedure using the toxic hexose analogue, 2-deoxy-D-glucose. Moreover, the two amino-acid-transport systems could not be induced in these mutants by hexoses. The capacity to phosphorylate hexoses was identical in mutants and in the wild-type strain. The loss of transport activities can be correlated with the loss of certain radiolabeled protein bands on fluorograms of sodium dodecylsulfate-polyacrylamide gels. These proteins are assumed to be responsible for the different transport systems in the wild-type strain. With the help of additional mutants defective in one or two of the different aminoacid-transport systems, it has been attempted to assign the different transport activities to individual protein bands on the gel.Abbreviations AUP arginine-uptake-defective mutant - 2-DG 2-deoxy-D-glucose - 6-DG 6-deoxy-D-glucose - HUP hexose-uptake-defective mutant - PUP^- proline-uptake-defective mutant - SDS sodium dodecyl sulfate - WT wild type