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At least 289 records · Page 16Linked to original sources
PubMed1976

[Regulation of glutamine metabolism in Chlorella pyrenoidosa. Mechanisms of regulating the activity of glutamine synthetase during ammonia assimilation].

Glutamine synthetase (GS) (E.C.6.3.1.2) activity in Chlorella cells decreased when NH4+ was added to nitrogen-free growth medium. This GS inactivation had such a rate, that it could not be due to the repression of enzyme synthesis: the GS activity decreased by 20% within 5 minutes of NH4+ assimilation. Glutamine content in cell increased in 2.5 times for this period. In vitro experiments have shown that glutamine is a strong inhibitor of GS from Chlorella grown in the presence of NO3-, and in a less degree--an inhibitor of GS from cells grown in ammonium-containing medium. The data obtained are negative with respect to possible mechanisms of GS activity regulation via adenylation and ATP-dependent destruction of glutamine synthetase.

Ammonia↗
PubMed2002

[Accumulation and biodegradation of anthracene by Chlorella protothecoides under different trophic conditions].

The bioaccumulation and degradation of anthracene by the green alage(Chlorella prothecoides) under autotrophic and heterotrophic conditions were studied. About 29% and 20% of anthracene(original concentration 1.0 mg.L-1) were degraded by light and by Chlorella protothecoides under the autotrophic condition, respectively. About 33.53% of anthracene (original concentration 2.5 mg.L-1) were degraded by C. protothecoides under the heterotrophic condition. The resistance and degradation ability of C. protothecoides under the heterotrophic condition was higher than that under the autotrophic conditions. More than 80% of residual anthracene was accumulated by algal cell under the two conditions. The bioaccumulation factor were 9064 and 1899, under the autotrophic and heterotropnic conditions, respectively. The net accumulation of anthracene, however, was much higher under the heterotropnic condition (202.29 micrograms) than that under the autotrophic condition (69.687 micrograms).

Anthracenes↗
PubMedDate not supplied

[Spectrophotometry of individual Chlorella cells].

A research of optical properties of individual microalgae Chlorella vulgaris cells was performed under various conditions of cultivation. On the basis of cell absorption spectra measurements in the visible spectrum region chlorophyll "a" absorption maxima are estimated to fall within the intervals of 669-675 nm for the red region of the spectrum and 429--436 nm for the blue one. Concentration of chlorophylls in the cells of the diameter from 2,8 up to 3,3 micrometers was found to increase considerably for algae grown both in continuous denisty static and periodical regimes. Integral optical density of individual Chlorella cells in the range of 400-750 nm grows with cell diameter increase. This increase appears to be most intensive in the cells grown in density static regime. A correlation was also established between algae cell dimensions and the general maxima position (correlation coefficient has a positive sign and absolute value near unit). With cell diameter growth the absorption maxima shift to the region of long waves.

Chlorella↗
PubMedDate not supplied

[Effect of light of different spectral composition on pigment accumulation, productivity and effectiveness of use of absorbed energy in photosynthesis during the developmental cycle of Chlorella].

The paper deals with the effect of light of different spectral composition on the duration of developmental cycle, pigment accumulation, productivity and efficiency of the use of absorbed energy in photosynthesis during the developmental cycle of Chlorella. An extremely high efficiency of using the green spectrum region in photosynthesis (21,0%) was observed. The efficiency of using absorbed radiation of the red (12%) and blue (6%) spectrum regions is also very high, but significantly lower than that of the green one. The activity of metabolic processes in Chlorella cells differs in various spectrum regions during different developmental cycles and is determined by the acting spectrum.

Chlorella↗
PubMedDate not supplied

[Physiological activity of Chlorella following exposure to space flight factors aboard the orbital station "Saliut"].

The photosynthetic activity of Chlorella vulgaris str. LARG-1 was studied after its dark exposure in the Tamiya medium to space flight factors enboard the Salyut orbital station. The exposure of Chlorella cells in the inactive state did not influence their basic physiological parameters (rate of growth and reproduction, cell size and population structure, chlorophyll content, cell viability) during subsequent intensive cultivation. These results show the possibility of storing the generative material of unicellular algae under the experimental conditions.

Cell Survival↗
PubMed2002

[The cell wall-degrading activities of lysin encoded by chlorella virus PBCV-1].

Lysin was isolated from Chlorella NC64A lysate which was infected by Chlorella virus PBCV-1. The enzyme property detection of lysin shows that it contains at least three enzyme activities: chitinase, chitosanase and beta-1, 3-Glucanase. This is consistent with the compose of Chlolrella cell wall. Chitinase and chitosanase, especially chitinase plays a important role in the process of virus entry. One 52 kD chitinase, one 56 kD chitosanase and one 36 kD chitosanase were obtained after purified by FPLC.

Cell Wall↗
PubMed2003

Failure of the biotic ligand and free-ion activity models to explain zinc bioaccumulation by Chlorella kesslerii.

Zinc accumulation by Chlorella kesslerii (Chlorophycee) was studied for [Zn2+] ranging from 4 pM to 1 mM. A first-order uptake flux as predicted by the free ion activity model (FIAM) and the biotic ligand model (BLM) was not observed. Furthermore, when algae were preconditioned in slightly limiting (10 pM) versus optimal (1 nM) free zinc concentrations, the internalization flux increased and was nearly constant over the range of [Zn2+] examined. This observation was attributed to the synthesis of membrane-bound zinc transporters. Neither solution Zn chemistry nor surface-bound Zn was a good predictor of Zn uptake fluxes. Several hypotheses were examined to explain the failure of the steady-state uptake models. Although zinc excretion and a Zn diffusion limitation were observed, neither result could explain the majority of observed deviation from the models. Bioaccumulation experiments performed with inhibitors (vanadate and carbonyl cyanide m-chlorophenylhydrazone [CCCP]) demonstrated clearly that zinc transport is an energy-dependent process in Chlorella kesslerii. The presence of an active transport signifies that Zn uptake may function independently of the electrochemical Zn gradient and that, in some cases, both uptake fluxes and receptor-bound Zn may be independent of solution chemistry.

Adsorption↗
PubMed2003

The effect of light:dark cycles of medium frequency on photosynthesis by Chlorella vulgaris and the implications for waste stabilisation pond design and performance.

The effect of light/dark (L:D) cycle times on the recovery from photoinhibition of green micro-alga Chlorella vulgaris (CCAP211/11c) and the cyanobacterium Synechococcus (CCAP1479/5) was investigated using an irradiated, temperature controlled oxygen electrode. The onset of photoinhibition in both organisms occurred at irradiances > 300 micromol m(-2)s(-1) at temperatures >15 degrees C. Light/dark cycle times were controlled independently using a relay timer and shutter placed between the quartz iodide light source and the oxygen electrode chamber. Oxygen evolution decreased rapidly when cells were continuously irradiated at 300, 500 and 750 micromol m(-2)s(-1). However, Chlorella cells irradiated at 300, 500 and 750 micromol m(-2)s(-1)on a L:D cycle of 60s:20s, 30s:60s and 60s: 120s respectively, maintained a constant rate of oxygen evolution over a 24 h incubation period. Exposure time to a given incident irradiance rather than the total light dose received appeared to determine the effect of light/dark cycle times on photosynthesis. A relationship was established between L:D ratio required to maintain constant oxygen production and incident photon flux density. The results suggest that the adverse effects of high irradiances on algae near the surface of a stratified waste stabilisation pond might be ameliorated by controlled mixing of algal cells through the depth of the pond.

Bioreactors↗
PubMedDate not supplied

[Early toxic effect of zinc, cobalt, and cadmium on photosynthetic activity of green alga Chlorella pyrenoidosa Chick S-39].

Early toxic effects of heavy metals (HMs) Zn, Co, and Cd in concentration from 0.01 to 100 mM on photosynthetic activity of the green alga Chlorella pyrenoidosa Chick S-39 were studied. The early effect of HMs was manifested as a rapid (0.5-2 h) reduction of photoinduced oxygen release by the algal cells. The suppressed relative yield of variable chlorophyll fluorescence ratio (Fv/Fm) by the metals as well as its dynamics in C. pyrenoidosa demonstrated rapid inactivation of photosystem II (PS II). Analysis of the induction curve of delayed chlorophyll fluorescence in Chlorella cells suggested that the early toxic effects of the tested concentrations of Zn, Co, and Cd included both reduced electron transport in PS II and decreased photosynthetic membrane energization. Hence, the early toxic effect of Zn, Co, and Cd was primarily related to the decreased efficiency of the light reactions of photosynthesis which further reduced the alga productivity later.

Cadmium↗
PubMed2003

Combined effect of concentrations of algal food (Chlorella vulgaris) and salt (sodium chloride) on the population growth of Brachionus calyciflorus and Brachionus patulus (Rotifera).

Salinity is an important variable influencing the density and diversity of rotifers. Studies on salt tolerance of rotifers have so far concentrated on euryhaline species while very little information is available on non-euryhaline taxa. In the present work, we have evaluated the combined effects of Chlorella vulgaris and sodium chloride on the population growth of two freshwater rotifers B. calyciflorus and B. patulus. A 24 hr acute tolerance test using NaCl revealed that B. calyciflorus was more resistant (LC50 = 3.75 +/- 0.04 g l-1) than B. patulus (2.14 +/- 0.09 g l-1). The maximal population density (mean +/- standard error) for B. calyciflorus in the control at 4.5 x 10(6) cells ml-1 (algal level) was 80 +/- 5 ind. ml-1, which was nearly a fifth of the one for B. patulus (397 +/- 7 ind. ml-1) under comparable conditions. Data on population growth revealed that regardless of salt concentration, the density of B. calyciflorus increased with increasing food levels, while for B. patulus, this trend was evident only in the controls. Regardless of salt concentration and algal food level, the day of maximal population density was lower (4 +/- 0.5 days) for B. calyciflorus than for B. patulus (11 +/- 1 day). The highest rates of population increase (r values) for B. calyciflorus and B. patulus were 0.429 +/- 0.012 and 0.367 +/- 0.004, respectively, recorded at 4.5 x 10(6) cells ml-1 of Chlorella in the controls. The protective role of algae in reducing the effect of salt stress was more evident in B. calyciflorus than B. patulus.

Animals↗
PubMed1991

Glucose increases the expression of the ATP/ADP translocator and the glyceraldehyde-3-phosphate dehydrogenase genes in Chlorella.

A presumably full-length cDNA clone of the mitochondrial ATP/ADP translocator (AAT) of Chlorella kessleri has been isolated and sequenced. The expression of the AAT gene is highly increased in the presence of D-glucose (14 mM). At least nine more genes are activated when autotrophically grown Chlorella cells switch to heterotrophic growth. Among these is the HUP1 gene coding for the hexose transporter (Sauer, N., Caspari, T., Klebl, F., and Tanner, W. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 7949-7952) and, as also shown in this paper, the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene. When glucose or the nonmetabolizable analogue 6-deoxyglucose is added to the cells, an increased expression of GAPDH or AAT is observed after 10 or 30 min, respectively. Hexose uptake mutants (HUP1-) do not respond to sugars in this way, which indicates that either the inducer has to be internalized or that the HUP1 translocator is part of the signal transduction mechanism.

Amino Acid Sequence↗
PubMedDate not supplied

[Comparative study of glutamate dehydrogenases of Chlorella].

The kinetic properties of the constitutive double specific glutamate dehydrogenase (NAD(P)--GDH) and the inducible NADP-specific glutamate dehydrogenase (NADP--GDH) of Chlorella pyrenoidosa Pringsheim 82T (thermophilic strain) in a deaminating reaction have been studied. NAD(P)-GDH behaves in a deamination as a Michaelis-Menten enzyme. NADP-GDH displays some lag-period before a steady-state phase. The duration of this lag depends on a substrate concentration. Besides that, an effect of all the substrates on a heat inactivation of both GDH and a product inhibition have been studied. All the substrates except the reduced co-factors protect effectively GDH from the heat inactivation, especially the thermolabille NADP-GDH. On the contrary, NAD(P)-H promote the heat inactivation of both GDH. The product inhibition analysis shows that the inducible NADP-GDH acts in vivo as a synthetic enzyme. In the previous paper (V. R. Shatilov et all., 1974, Dokl. Acad. Nauk USSR, 216,223) it was shown for the constitutive GDH that p-CMB strongly inhibited a desamination and slightly (if any) affect an amination. It this paper it is shown that action of p-CMB on the amination depends on the presence of NAD+ (not NADP+ or L-glutamate). p-CMB and NAD+ affect tha amination in a strongly sunergetic manner. Some suggestions about the intracellular localization of chlorella GDH are made.

Chlorella↗
PubMed1978

[Irreversible inactivation of Chlorella glutamine synthetase by urea].

The effect of urea on Chlorella glutamine synthetase (E. C. 6.3.1.2) activity and tertiary structure is investigated. Urea is found to inhibit the activity of glutamine synthetase, the inhibitory effect being independent on the time. The enzyme molecule relax and changes its affinity to ammonium under the effect of urea at concentrations of 1.0-4.0 M. Higher concentrations of urea (5,0 M and more) produce a dissociation of the enzyme molecule into monomers without any intermediate forms. Monomers do not possess any synthetase and transferase activities. Substrates and cofactors do not protect the enzyme from the effect of urea and do not stimulate the emzyme reactivation and reaggregation after its dissotiation. The data obtained are discussed from the viewpoint of the regulation of Chlorella glutamine synthetase activity in vivo.

Animals↗
PubMedDate not supplied

[Production of glycolic acid by the cells of Chlorella pyrenoidosa].

The maximum production of glycolic acid by the cells of Chlorella pyrenoidosa, strain S-39, was found when the cells, grown at the content of carbon dioxide of 2% in the air and illumination of 2000 lx, were transferred to 10(-3) M phosphate buffer (pH 7.0) with barbotage by pure oxygen and illumination of 30,000 lx. The rate of production of glycolic acid during the first five minutes is the same in the light and darkness; later no glycolate is formed in the darkness while in the light glycolate is formed at a lower rate. Bicarbonate inhibits production of glycolate. Negative interaction has been established between oxygen and bicarbonate during their effect on the production of glycolic acid. These data confirm the production of glycolic acid in the cells of Chlorella pyrenoidosa from ribulose diphosphate which is oxidized by molecular oxygen with the participation of ribulose diphosphate carboxylase acting as an oxygenase.

Bicarbonates↗
PubMed1988

Effect of lipophilic extract of Chlorella vulgaris on alimentary hyperlipidemia in cholesterol-fed rats.

The effect of glycolipid (GL) and phospholipid (PL) fractions obtained from Chlorella on serum lipid level and fecal excretion of steroids were examined in cholesterol-fed rats. The increase of the level of serum lipids were inhibited by the feeding of GL, PL and Chlorella powder almost the same degree. Fecal excretion of steroids (mostly of cholesterol, deoxycholic and lithocholic acid) were increased by feeding of GL and PL fractions. It is concluded that the feeding of each fraction inhibits the absorption of exogenous steroids and promotes turnover of bile acids in liver to suppress the increase of serum cholesterol level caused by administration of high cholesterol diet.

Animals↗
PubMed1976

Studies on the purification of wastewater from the nitrogen fertilizer industry by intensive algal cultures. I. Growth of Chlorella vulgaris in wastes.

The possibility of growth of intensive cultures of Chlorella vulgaris on industrial wastewater from nitrogen fertizer plant containing ammonia, urea and nitrate was investigated. Good growth of algae was obtained when the waste was enriched with phosphorus and inoculum contained a high number of cells. The optimal pH for the culture was 7.0--8.0. The main factor limiting growth of algae on wastes on the concentration of ammonia nitrogen. Chlorella vulgaris grows quite well in wastes containing 600 mg NH4-N/l but is inhibited at concentration about 100 mg NH4-N/l.

Ammonia↗
PubMed1981

Kinetic mechanism of assimilatory NADH:nitrate reductase from Chlorella.

Chlorella nitrate reductase catalyzes the reduction of nitrate to nitrite by NADH. Initial velocity studies showed that the kinetic mechanism is sequential, indicating that both substrates must bind to the enzyme before any products are released. Product inhibition with NAD and nitrite showed that competitive inhibition was observed when the inhibitor was similar to the varied substrate, while noncompetitive inhibition was observed when the inhibitor was dissimilar to the varied substrate. Likewise, dead-end inhibition with adenosine 5'-diphosphoribose and thiocyanate showed competitive inhibition when the inhibitor was similar to the varied substrate and noncompetitive inhibition when the inhibitor was dissimilar to the varied substrate. These results indicate that Chlorella nitrate reductase follows a random bi bi kinetic mechanism. Phosphate was found to stimulate NADH:nitrate reductase activity and 2-fold. The NADH:cytochrome c reductase activity associated with nitrate reductase was not affected by phosphate suggesting the effect of phosphate is on the nitrate-reducing moiety of the enzyme. Phosphate increases Vmax but has no effect on the apparent Km for nitrate.

Anions↗