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PubMed1977

Possible role of cyclic AMP in the synthesis of chlorophyll in Chlorella fusca.

The intracellular concentration of cAMP in the green alga Chlorella fusca was in the range of 2.10(-9) to 10(-8) moles/g dry weight and was strongly dependent on the growth conditions. The cAMP level was high with high light intensity, low nitrate or glucose concentration. Intracellular cAMP increased only by factor of 2 when high amounts (up to 10(-3) M) of cAMP were added to the medium. Most of the given cAMP was converted to 5'-AMP. Addition of cAMP had little effect on the chlorophyll content of the cells, only at 10(-6) M some enhancement in photoautotrophic cultures was observed. On the other hand high amounts of cAMP in the medium increased the growth rate. DBcAMP* showed a positive effect on chlorophyll synthesis and growth rate at much lower concentrations compared to cAMP. Stimulation effects of exogenous cAMP on the synthesis of chlorophyll were also observed in mixotrophic cultures with a high glucose/nitrate ratio, conditions where chlorophyll synthesis is repressed. Similar to autotrophic conditions DBcAMP was more effective than cAMP. These data indicate that cAMP may act in a system controlling the chlorophyll content of the cells in response to nutrients or light.

Chlorella↗
PubMed1975

Physiological and biochemical contributions to the taxonomy of the genus Chlorella. X. Products of glucose fermentation.

The products of glucose fermentation were studied in 87 strains of the genus Chlorella. Lactic acid, acetic acid, formic acid, glycerol, ethanol, H2 and CO2 were identified. The lactic acid was shown to be D(minus)lactic acid. The pattern of fermentation produces is species-specific and can therefore be used as a taxonomic character. Lactic acid was found in C. fusca (varieties vacuolata, fusca, and rubescens), C. zofingiensis, C. vulgaris (var. vulgaris and f.tertia), and C. protothecoides. Formic acid and H2 appeared in those species which contain hydrogenase. Rather large amounts of glycerol were produced only by the most salt-tolerant species C. luteoviridis, C. saccharophila, and C. protothecoides.

Acetates↗
PubMed1975

The chloroplastic DNA of Chlorella pyrenoidosa (Emerson strain): heterogeneity and complexity.

The heterogeneity and the complexity of Emerson strain Chlorella pyrenoidosa chloroplastic DNA have been investigated by means of thermal denaturation and renaturation kinetics, and the results have been compared with those of the strain 211/8b of the same alga. The thermal denaturation properties are very close to those of the other strain: the Tm of 65 degrees C in 0.1 standard saline citrate, the maximal hyperchromicity of 41%, and the dispersion coefficent delta 2/3 of 6.65 degrees C. The first derivated curves of the melting profiles show also five components. Denatured chloroplastic DNA renatures rapidly. Two fractions are found; their kinetic complexities have been estimated: 1.5 times 10(7) daltons for the fast renaturing fraction; 2x 10(8) daltons for the low d (G + C) content of the chloroplastic DNA: 1.24 times 10(8) daltons). The unique nucleotide sequence is present in about 19 copies per chloroplastic genome. This report confirms the homogeneity of the chloroplastic genome of algae.

Centrifugation, Density Gradient↗
PubMed1976

[The metabolic interactions between Paramecium bursaria Ehrbg. and Chlorella spec. in the Paramecium bursaria-symbiosis. II. Symbiosis-specific properties of the physiology and the cytology of the symbiotic unit and their regulation (author's transl)].

The endosymbiotic association of Paramecium bursaria Ehrbg. with Chlorella spec. (green Paramecium) was studied both physiologically and cytologically. Comparison of the properties of the symbiotic unit with those of the symbiotic partners which had been isolated from it revealed the following features and differences: 1. Up to 6000 lux the photosynthetic capacity of the symbiotic unit is higher than that of the isolated symbiotic algae grown independently in mass culture under defined conditions. Alga-free Paramecium bursaria (colourless Paramecium) show a very low rate of CO2-fixation. 2. The green Paramecium has a higher compensationpoint of photosynthesis (4000-5000 lux) than the isolated alga (200-400 lux). 3. Green paramecia consume less oxygen in darkness than colourless organisms but more than the isolated algae. 4. The uptake of carbohydrates from the culture medium by green parpmecia is lower than the uptake by alga-free P. bursaria but higher than the one of the isolated algae. 5. Symbiotic algae within the intact symbiotic unit show tightly packed photosynthetic membranes and an intense disposition of starch. In the presence of 3-(3,4-Dichlorophenyl)-1,1-dimethylurea (DCMU) or in darkness the arrangement of thylakoids is less compact and the deposition of starch is reduced. The growth and the number of the symbiotic algae in situ is regulated by a complex mechanism to which the intracellular level of carbohydrates belongs. The results are discussed in connection with ecological aspects of the Paramecium bursaria-endosymbiosis.

Animals↗
PubMed1975

[Effect of blue and red light on the synthesis of ribosomal RNA in Chlorella].

In autotrophic cultures of Chlorella pyrenoidosa (strain 211-8b) incorporation of tritiated guanosine and uridine into ribosomal RNA is stimulated by light. Blue light of wavelengths around 457 nm is considerably more effective than red light around 679 nm (5-10(-10) Einstein cm-2 sec-1 for both). This effect can be demonstrated for young daughter cells (at the end of the dark period) and for older cells (at the end of the light period). It is shown to depend on a regulation of rRNA-synthesis. The blue light dependent enhancement of incorporation is more pronounced in the cytoplasmic rRNA (25 and 18 s) than in the chloroplast rRNA (23 and 16 s). Blue light of low intensity (1-10(-10) Einstein cm-2 sec-1) has nearly the same effectivity as the fivefold intensity, whereas red light of equal quantum fluxes enhances incorporation only slightly compared with the dark control. The blue light dependent enhancement of rRNA-synthesis continues in the following darkness in contrary to that caused by red light. This enhancement is also found in DCMU-poisened cultures. In contrast to this, is red light in presence of DCMU, incorporation into rRNA is nearly the same as in dark. It is concluded that the regulation of rRNA-synthesis in red light is closely connected to complete photosynthesis, while in blue light an additional regulation takes place independent of photosynthesis.

Chlorella↗
PubMed1978

The role of vanadium in green plants. IV. Influence on the formation of delta-aminolevulinic acid in Chlorella.

In a series of experiments, it is demonstrated that the trace element vanadium (4.10(-7) g-at/1 as NH4VO3) has a considerable positive influence on the synthesis of delta-aminolevulinic acid(delta-ALA) in the autotrophically growing green alga Chlorella pyrenoidosa, the effect being visible by an enhanced output of the amino acid into the culture medium in presence of levulinic acid (LA). The level of intracellularly accumulated delta-ALA, however, is not changed in presence of the metal. The V-effect on exogenous found delta-ALA is suppressed, when LA is added to the nutrient medium at low pH (pH5), although V-uptake into the algal cells is not disturbed by LA. As demonstrated in culture media with various nitrogen sources (urea, partially hydrolized urea, ammonium salts), the development of the pH during the cultivation time is important for the presentation of the V-effect on delta-ALA. It is suggested that vanadium acts as a catalyst in the conversion of 4,5-dioxovaleric acid to delta-ALA by transamination.

Aminolevulinic Acid↗
PubMed1996

Impact of aluminium, fluoride and fluoroaluminate complex on ATPase activity of Nostoc linckia and Chlorella vulgaris.

This study demonstrates a pH-dependent inhibition of Mg(2+)- and Ca(2+)-ATPase activities of Nostoc linckia and Chlorella vulgaris exposed to AlCl3, AlF3, NaF and AlCl3+NaF together. AlF3 and the combination of AlCl3+NaF were more inhibitory to both the enzymes as compared with AlCl3 and NaF. Toxicity of the test compounds increased with increasing acidity. Interaction of AlCl3+NaF was additive on N. linckia and C. vulgaris, respectively, at pH 7.5 and 6.8, and synergistic at pH 6.0 and 4.5. In the presence of 60 and 100 microM PO4(3-) an increased NaF concentration (in the AlCl3+NaF combination) was required to produce the same degree of inhibition in ATP synthesis and ATPase activity. Toxicity of fluoroaluminate was reduced in the presence of EDTA and citrate. Except for beryllium to some extent, combinations of cadmium, cobalt, iron, manganese, tin and zinc with fluoride were not as effective as aluminium in inhibiting the ATPase activity. The presence of a 100 kDa protein band in SDS-PAGE of both control as well as AlCl3+NaF-treated samples suggested that AlF4- inhibits the ATPase activity by acting as a functional barrier without affecting the structure of the enzyme.

Adenosine Triphosphatases↗
PubMedDate not supplied

Measurement of manganese amelioration of cadmium toxicity in Chlorella pyrenoidosa using turbidostat culture.

Cadmium (Cd) toxicity and amelioration of Cd toxicity by Mn were measured in Chlorella pyrenoidosa, using turbidostat culture. The responses were measured in terms of the maximum specific growth rate, mu max, of the populations. In turbidostat culture mu max is a dependent variable that can be measured continuously. Cd (as CdCl2.2.5 H2O) was added to control populations at a concentration of 1.8 microM Cd. Toxicity was expressed after a 5 generation lag and resulted in a mu max steady state 62% lower than the initial control after 2 generations. With continued Cd exposure, Mn (as MnCl2.6H2O) was then added stepwise to a concentration of 10.4 microM Mn which caused a rapid, immediate increase in mu max followed by linear increase until a steady-state plateau was reached at a mu max 90% of control. The ameliorative response spanned 20 culture generations. After addition of Mn (10.4 microM), cellular Cd concentration did not change and cellular Mn concentration increased. Increase in mean cell size accompanied Cd exposure and was significantly decreased when supplemented with 10.4 microM Mn. Possible mechanisms of the amelioration are discussed.

Cadmium↗
PubMed1993

The growth response of the green alga Chlorella vulgaris to combined divalent cation exposure.

Using the growth response of the green alga Chlorella vulgaris as a model system, the effects of combinations of the environmentally active cations Cd, Co, and Cu were evaluated. The 96-h static EC50 for these cations to C. vulgaris were, respectively, 0.89 microM, 9.0 microM, and 2.8 microM, yielding a toxicity series such that Cd > Cu > Co. The cation combinations of Cd + Cu, and Cu + Co acted synergistically, while Cd + Co, and the tri-metallic combination Cd + Cu + Co resulted in antagonistic interactions. Examination of these toxic combinations at 24, 48, 72, and 96 h indicate that the cellular response is not a uniform one. Failure of energy dispersive X-ray spectrophotometric analysis to demonstrate any intracellular incorporation of these cations (except for a weak cytoplasmic Cu peak at the 8.0 KEV position) suggests that the toxic actions of these cations at EC50 concentrations are exerted at the level of the plasma membrane.

Cadmium↗
PubMed1991

The effects of pH on the growth of Chlorella vulgaris and its interactions with cadmium toxicity.

The effects of pH alone, and in combination with exposure to 0.89 microM cadmium, on the growth response of the green alga Chlorella vulgaris were evaluated. Acidic (3.0-6.2) and alkaline (8.3-9.0) pH values retarded the growth of this alga. Optimal growth occurred when the pH of the medium was adjusted to values of 7.5 and 8.0. When the cells were exposed to pH adjusted medium plus the presence of 0.89 microM Cd, a value known to reduce population growth by 50% at the control pH of 6.9, the affects were additive at the acidic (3.0-5.0) pH ranges. At alkaline pH values of 8.3-9.0 all toxicity responses could be explained by pH adjustment alone, indicating that additional cadmium toxicity was absent. At pH values of 7.5 and 8.0, cadmium toxicity was mitigated against, and resultant growth at pH 8.0 was at the same enhanced rate as this pH without cadmium.

Cadmium↗
PubMed1990

Impact of bimetallic combinations of Cu, Ni and Fe on growth rate, uptake of nitrate and ammonium, 14CO2 fixation, nitrate reductase and urease activity of Chlorella vulgaris.

The toxicity of Cu, Ni and Fe individually, as well as in combination (Cu + Ni, Cu + Fe, Ni + Fe), on growth-rate depression, uptake of NO3- and NH4+, photosynthesis, nitrate reductase and urease activity of Chlorella vulgaris has been studied. All the test metals when used individually showed pronounced toxicity on all the parameters studied. However, their interactive effect was mostly antagonistic except for Cu + Ni (synergism). Pre-addition of Fe offered more protection to the cells against copper and nickel toxicity. The data of statistical analysis reconfirmed that 14CO2 uptake is the most sensitive parameter (significant at P less than 0.005, both for time and treatment) than others in metal toxicity assessment. However, these results suggest further that exposure time and sequence of metal addition are very important in biomonitoring of heavy metal toxicity.

Ammonia↗
PubMed1993

Ultrastructural studies on a chlorella virus from Germany.

This is the first report on the morphology and fine structure of chlorella virus Göttingen-1 (CVG-1), an European member of the newly approved family Phycodnaviridae, which infects certain unicellular, eukaryotic, exsymbiotic, green algae. CVG-1 are polyhedral particles 145-160 nm in diameter. The capsid consists of two shells, apparently composed of ca. 7 nm subunits. Whereas the outer shell of the capsid appears to be icosahedral, the inner shell appears to be irregular underneath one vertex of the virion. In this vertex the inner shell is separated from the outer shell leaving a distinct space ("empty vertex") of unknown function.

Capsid↗
PubMed1976

Effect of hexachlorobenzene on some growth parameters of Chlorella pyrenoidosa.

Chlorella pyrenoidosa was incubated with HCB (0.001-10.0 ppm) in a "light-thermostat" at 30 degrees C for 46 h with continuous light (4000 Lux) and aeration. HCB decreased growth as deduced from measurements of chlorophyll content, dry matter, carbohydrate content, and total nitrogen. Incubation with HCB for three months in Erlenmeyer-flasks resulted in an increase of chlorophyll over control value in cultures receiving 0.1 and 1.0 ppm HCB. After transfer of the cultures from Erlenmeyer-flasks to growth conditions of a "light-thermostat", growth of the algae was greatly enhanced by all HCB concentrations studied; a concentration of 0.1 ppm being most effective.

Carbohydrate Metabolism↗
PubMed1990

Enhanced resistance against Escherichia coli infection by subcutaneous administration of the hot-water extract of Chlorella vulgaris in cyclophosphamide-treated mice.

The effects of Chlorella vulgaris extract (CVE-A) on the recovery of leukocyte number and the augmentation of resistance to bacterial infection were examined in CDF1 mice made neutropenic by cyclophosphamide (CY). They were treated intraperitoneally with CY (150 mg/kg) on day 0, and were given CVE-A (50 mg/kg) subcutaneously (s.c.) every other day from day 1 to day 13 after CY treatment. CVE-A accelerated the recovery of polymorphonuclear leukocytes (PMN) in the peripheral blood in CY-treated mice. The number of granulocyte/monocyte-progenitor cells (CFU-GM) in the spleen increased rapidly and highly after the administration of CVE-A in CY-treated mice, in contrast to the absence of change due to CVE-A in the number of bone marrow cells in CY-treated mice. Administration of CVE-A in CY-treated mice enhanced the accumulation of PMN in the inflammatory site and the activity of the accumulated leukocyte cells in luminol-dependent chemiluminescence. The mice became highly susceptible to an intraperitoneal infection with E. coli on day 4 after CY treatment, whereas the mice given CVE-A showed an enhanced resistance against E. coli infection, irrespective of the timing of challenge. The bacterial number in CY-treated mice increased explosively after inoculation, resulting in death within 24 h. A progressive elimination of bacteria was observed from 6 h in the peritoneal cavity, spleen and liver of CY-treated mice given CVE-A s.c. These results indicate that CVE-A can be used as a potent stimulant of nonspecific resistance to infection in neutropenic mice.

Animals↗
PubMed1977

Partial enzyme digestion studies on Escherichia coli, Pseudomonas, Chlorella, Drosophila, HeLa and yeast 5S RNAs support a general class of 5S RNA models.

Fox and Woese (1975a) have shown that a model of 5S RNA secondary structure similar to the one originally derived for Chlorella 5S RNA can be generalized with relatively minor variations to all sequenced 5S RNA molecules, i.e. that corresponding base paired regions can be formed at approximately the same positions. We present experimental data in favour of this hypothesis and show that the points at which ribonucleases T1, T2 and pancreatic ribonuclease cleave six different 5S RNA molecules under 'mild' conditions (high ionic strength, low temperature, low RNAase concentration) nearly always fall in the proposed single-stranded regions. We conclude that this model is a good approximation to the conformation of 5S RNA in solution.

Base Sequence↗
PubMed1996

The chloroplast chlL gene of the green alga Chlorella vulgaris C-27 contains a self-splicing group I intron.

The chlL gene product is involved in the light-independent synthesis of chlorophyll in photosynthetic bacteria, green algae and non-flowering plants. The chloroplast genome of Chlorella vulgaris strain C-27 contains the first example of a split chlL gene, which is interrupted by 951 bp group I intron in the coding region. In vitro synthesized pre-mRNA containing the entire intron and parts of the flanking exon sequence is able to efficiently self-splice in vitro in the presence of a divalent and a monovalent cation and GTP, to yield the ligated exons and other splicing intermediates characteristic of self-splicing group I introns. The 5' and 3' splice sites were confirmed by cDNA sequencing and the products of the splicing reaction were characterized by primer extension analysis. The absence of a significant ORF in the long P9 region (522 nt), separating the catalytic core from the 3' splice site, makes this intron different from the other known examples of group I introns. Guanosine-mediated attack at the 3' splice site and the presence of G-exchange reaction sites internal to the intron are some other properties demonstrated for the first time by an intron of a protein-coding plastid gene.

Amino Acid Sequence↗
PubMed1981

Effect of dilution rate, pH and temperature on the growth of Chlorella kessleri in a continuous autotrophic culture.

In a culture of Chlorella kessleri illuminated with a sodium vapour lamp at 33 degrees C and pH 6.5 the maximum rate of biomass production was 4.5 g L-1 d-1. Of the total volume of 3.6 L or the suspension 2.5 L were placed between two glass concentric cylinders surrounding the tube. Examples of the course of specific growth rate mu in the transient state following jump changes in the dilution rate, pH and temperature are presented. After a jump change of pH or temperature of the suspension maximal and minimal values, respectively, of mu are observed.

Chlorella↗