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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 78 (1971), S. 214-223 
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Das Verhalten von Chlorella fusca gegenüber markiertem Chlorat und Perchlorat wurde untersucht. Unabhängig von den Bedingungen wird Perchlorat nur zu einem geringen Maß aufgenommen, und es wird nicht zu Chlorid reduziert. Dagegen wird Chlorat mit Michaelis-Menten-Kinetik reduziert. Die Geschwindigkeit wird durch Belichtung erhöht und durch DNP, Cyanid und Jodacetat vermindert. Die Reduktion des Chlorats wird durch Nitrat und Nitrit kompetitiv gehemmt. Offenbar erfolgen Aufnahme und Reduktion von Chlorat durch Mechanismen, die dem Stoffwechsel von Nitrat und Nitrit dienen. Nach Züchtung auf Ammonium als einziger Stickstoffquelle reduziert Chlorella anfangs Chlorat nicht. Die Dunkelreduktion durch nitratgezüchtete Chlorella wird durch eine stickstofffreie Vorperiode beschleunigt.
    Notes: Summary The reactions of labelled chlorate and perchlorate with Chlorella fusca have been studied. Independently of conditions, perchlorate is absorbed only to a small extent, and it is not reduced to chloride. In contrast, chlorate is reduced with Michaelis-Menten kinetics. The velocity of reduction is higher in the light than in the dark, and is depressed by DNP, cyanide and iodoacetate. The reduction of chlorate is competitively inhibited by nitrate and nitrite. Apparently uptake and reduction of chlorate are mediated by mechanisms evolved for nitrate and nitrite metabolism. Chlorella grown on ammonium as the only nitrogen source at first does not reduce chlorate. The velocity of reduction in the dark by nitrate-grown Chlorella is enhanced by a period without nitrogen before the test.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 86 (1972), S. 281-290 
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Der freie Raum innerhalb der Zellwand von Chlorella fusca wurde nach einer Verdünnungsmethode mit 14C-mannit bestimmt. 36Cl-Perchlorat ist wegen des Donnan-Effekts weniger geeignet. Korrektur für außen anhaftendes Wasser wurde mit 14C-Dextran durchgeführt. Während der Lichtphase (16 Std) des Wachstumscyclus nimmt der freie Raum von 11 auf 4% des Zellvolumens ab, und er nimmt während der ersten 8 Std der Dunkelphase (12 Std) wieder zu. Während der Lichtphase vermindert sich, nach dem Volumen des freien Raums zu urteilen, die Zellwanddicke; offenbar bleibt die Zellwandsynthese gegenüber dem Zellwachstum zurück.
    Notes: Summary The free space in the cell wall of Chlorella fusca has been determined by a dilution method with 14C-mannitol. Owing to a Donnan effect, 36Cl-perchlorate is less suitable, 14C-dextran was used to correct for external water. During the light phase (16 h) of the generation cycle, the free space decreases from 11 to 4% of the cell volume. It increases again during the first 8 h of the dark phase (12 h). During the light phase, the cell wall, as judged by the free space volume, thins; apparently cell wall synthesis does not fully kepp in step with cell growth.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 129 (1981), S. 325-330 
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Anacystis ; Chloride transport ; Membrane potential ; ATP level
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chloride uptake by the cyanobacterium Anacystis nidulans at 38°C is energy dependent showing maximum rate (around 5.10-7 mol Cl-xml cell water-1xmin-1) and accumulation (up to 160 fold) in light and air. The respective values in air and darkness were 40–70% lower. In the dark under N2 no uptake was found. Chloride transport had an optimum at pH 6.7 and a K M of 2.10-5 M which was pH-independent. It was inhibited by carbonyl cyanide m-chlorophenylhydrazone and N,N′-dicyclohexylcarbodiimide in the light and in the dark, and also to a lesser extent by valinomycin. 3-(3,4-dichlorophenyl)-1,1-dimethylurea in the light caused a moderate stimulation. To obtain information about the energy source of active chloride transport the action of the four inhibitors on membrane potential (determined through the distribution of triphenylmethylphosphonium) and ATP level (determined by the firefly method) was examined. It was found that a high negative membrane potential was unfavorable for chloride accumulation probably by stimulating passive efflux. On the other hand a good correlation between ATP level and chloride transport activity was obtained. Attempts to induce chloride uptake by sudden acidification of the external medium in presence of N,N′-dicyclohexyl-carbodiimide or during anaerobiosis were not successful. Two mechanisms of chloride uptake are discussed: a) primary active transport by an ATP-dependent pump, and b) “chemiosmotic” secondary active transport linked to a proton gradient, the present data favoring mechanism a.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 6 (1983), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. The effect of CO2 on net K+ uptake by Chlorella fusca grown on high CO2 levels was examined by passing 1.5% CO2 through algal suspensions gassed previously with air or CO2-free air Addition of CO2 in the light caused a large net uptake of K+ (initial velocity 4.2–9.2 mmol s−1 m−3 cells) which decreased the concentration of K+ in the supernatant from 0.1–0.2 mol m−3 to 3–10 mmol m−3. In the dark and in the presence of 30 mmol m−3 DCMU, no effects were found.Measurement or the unidirectional K+ fluxes by using 86Rb+ as a label showed that in the presence of 1.5% CO2, influx of K+ was increased by a factor of 2–4 while efflux was inhibited completely.CO2 hyperpolarized the membrane potential (determined through TPP+ uptake) from –120mV to –130 mV which could not explain the more than 15,000-fold K+ accumulations.In the light, CO2 lowered the intracellular pH (determined with DMO) by 0.5 units. In the dark and in the presence of DCMU only, a small acidification of 0.1 units was found.During the first 15 min after addition of CO2 the malate content of the cells increased from 0.7 to 1.5 mol m−3 packed cells.On the basis of these and earlier results, CO2-induced net K+ uptake is interpreted as a stimulation of an electroneutral ATP-dependent K+/H+ exchange at the plasmalemma. This exchange acts as a ‘pHstat’ by reducing the intracellular acidification caused by production of acidic assimilation products.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Planta 117 (1974), S. 339-348 
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The Na metabolism of Chlorella fusca at high pH values was investigated by radiotracer methods. The Na influx into Chlorella is strongly (20–30 fold) enhanced in 5·10-3M NaOH (pH 11,4). It then approaches the rate of the influx of K (labelled with 86Rb). The rise of the Na influx begins at pH 8.3 and has a point of inflection at pH 8.7. The cells remain undamaged. Na uptake from 5·10-3M NaOH leads to a steady state with a 10-fold Na accumulation. The cells then contain 20–30 times more Na than in a neutral medium. The Na efflux remains proportional to the Na concentration in the cell. The Na uptake at high pH is energy-dependent, has saturation kinetics (K M =2·10-3 mol/l) and is competitively inhibited by K. During Na uptake at high pH an equal amount of K is released from the cells. It is assumed that the enhancement of Na influx in NaOH is due to the fact that the selectivity for K of the membrane-bound K transport system is lowered under the alkaline conditions. Possibly an SH group is involved in this alteration. Neutralisation after Na accumulation from NaOH is followed by energy-dependent net Na efflux. An active Na efflux pump with first order kinetics is postulated. This pump can exchange Na against K and H. It is stimulated by external K, but can work without it.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Planta 138 (1978), S. 243-248 
    ISSN: 1432-2048
    Keywords: Chlorella ; Permeant acids and bases ; pH-stat ; Potassium uptake ; Proton transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Salts of membrane-permeant acids and bases strongly influence net K uptake by Chlorella fusca. Na phenylacetate, acetate, isobutyrate, propionate, and butyrate added to buffered algal suspensions containing 0.1–0.2 mM KCl increasingly stimulated net K uptake. In contrast, K release was induced by the chlorides of imidazole, ammonia and methylamine. All these effects were found in the light and, less pronounced, in the dark. The dependence of the net K movements on the concentrations of the salts added and on the pH of the medium suggests that the free acids or bases are the effective agents. Between net uptake of K and uptake of labeled propionate a molar ratio close to 1 was found. It is concluded that the internal pH of the cell is changed by the permeants. Acidification of the cytoplasm stimulates extrusion of protons coupled to uptake of K. Alcalization brings about proton uptake and K extrusion. Apparently K/H exchange serves as a pH-stat of the cell.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Planta 156 (1982), S. 10-15 
    ISSN: 1432-2048
    Keywords: ATP level ; Chlorella ; Chloride transport ; Intracellular pH ; Membrane potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Active Cl- uptake by Chlorella fusca was examined by using 36Cl as a label. Under light/air conditions chloride influx from a 2.4·10-5 M solution was 4.0±0.04 nmol m-2s-1. After 70±10 min a stationary 380±40 fold accumulation was reached. In dark/air and dark/argon influx and accumulation were reduced to 25±6%, respectively, 5±1.5% of the light/air control. Cl- uptake had a broad optimum around pH 7 and showed saturation kinetics with a K M of 1.25·10-5 M and a v max of 7.0 nmol m-2s-1 in light/air. Br- inhibited Cl- uptake strongly, J-, ClO 4 - , SO 4 2- , and NO 3 - had no inhibitory effect. Inhibitor studies with carbonyl cyanide m-chlorophenylhydrazone and N,N′-dicyclohexylcarbodiimide resulted in a good correlation between Cl- uptake and ATP level. 3-(3,4-Dichlorophenyl)-1,1-dimethylurea and darkness reduced transport activity without affecting the ATP level. The magnitudes of the pH gradient and the membrane potential across the cell membrane were determined and/or estimated under different conditions. It could be shown that in Chlorella Cl- transport cannot proceed via secondary active H+/Cl- cotransport. In addition, 2H+/Cl- cotransport seems unlikely for energetic reasons. On the basis of the results of this and the following study, a primary active ATP-driven Cl-/OH- exchange pump is proposed.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Planta 156 (1982), S. 16-20 
    ISSN: 1432-2048
    Keywords: Acid, permeant ; Carbon dioxide ; Chlorella ; Chloride transport ; Glucose (and CL- transport)-pH ; intracellular
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Glucose at 5 mM inhibited chloride uptake by Chlorella fusca in the light and in the dark by 30±10% and acidified the cell interior by 0.2 units (measured with 5.5-dimethyl-oxazolidine-2.4-dione; DMO). Neither effect was shown by the glucose analogues 3-O-methylglucose and 6-desoxyglucose which are transported into the cell but not metabolized. As it was surmised that inhibition of Cl- transport was the result of intracellular acidification, the action of other agents on Cl- transport and intracellular pH was examined. The Tris salts of the permeant acids DMO and propionic acid inhibited Cl- transport. The concentration and pH dependence of this effect were consistent with the free acids being the effective agents. At pH 6.7 the 15 mM Tris salts has about the same effect on Cl- transport as 5 mM glucose. Under these conditions the intracellular pH (measured by the DMO method) was lowered by 0.2 units with glucose as well as, in presence of the Tris salts. When the algae were gassed with 1.5% CO2 in air, Cl- uptake in the light was depressed to 40–50% and the intracellular pH was lowered by 0.4 units. On the basis of these observations and the results from the preceding study, inhibition of Cl- transport by glucose is interpreted as inhibition of an ATP-dependent Cl-/OH- exchange by intracellular acidification, due to glucose metabolism.
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  • 9
    ISSN: 0005-2736
    Keywords: (C. fusca) ; Base transport ; Potassium/proton antiport ; Proton transport ; pH regulation ; pH, intracellular
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0005-2728
    Keywords: (Chlorella fusca) ; ATP level ; Intracellular pH ; K^+ transport ; Proton transport ; Uncoupler
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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