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The Assimilation of Ammonia by Nitrogen-starved Cells of Chlorella vulgaris: Part I. The Correlation of Assimilation with Respiration 总被引:1,自引:0,他引:1
The addition of ammonium sulphate to a suspension of nitrogen-starvedChlorella cells is followed immediately by the rapid assimilationof ammonia and a large increase of the respiration rate. Theassimilation of ammonia and the high rate of respiration continueuntil either all the ammonia has been assimilated or some carbonreserve within the cells has been exhausted. Which happens firstdepends on the amount of ammonia added and the quantity of cellspresent. The respiration which accompanies, ammonia assimilationis sensitive to cyanide and it has a respiratory quotient of075 compared with 1213 for normal reapiration.The addition of glucose to nitrogen-starved cells when ammoniais being assimilated does not increase either the rate of respirationor the rate of assimilation. The rates of reapiration and ammoniaassimilation by normal cells are markedly increased by the additionof glucose. Light has little effect on the rate of ammonia assimilationby nitrogen-starved cells, but doubles the assimilation rateof normal cells. 相似文献
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The Assimilation of Ammonia and Nitrate by Nitrogen-Starved Cells of Chlorella vulgaris 总被引:3,自引:0,他引:3
P. J. Syrett 《Physiologia plantarum》1956,9(1):28-37
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The Assimilation of Ammonia and Nitrate by Nitrogen- Starved Cells of Chlorella vulgaris 总被引:1,自引:0,他引:1
P. J. Syrett 《Physiologia plantarum》1955,8(4):924-929
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The Assimilation of Acetate by Chlorella vulgaris 总被引:2,自引:0,他引:2
The acetate metabolism of autotrophically grown, acetate-adaptedand acetate-grown cells is compared. All oxidize acetate rapidlyand assimilate about half of the acetate added in short-termexperiments. Kinetic analysis of the incorporation of 14C-acetatereveals citrate as a primary product of acetate assimilationin all cells in darkness. Malate formed from acetate-I-14C byacetate-grown cells is asymmetrically labelled in a manner consistentwith a primary incorporation of acetate into malate by a malatesynthase reaction. The chief difference between autotrophic and acetate-grown cellsis the faster rate at which the latter incorporate acetate carboninto compounds outside the tricarboxylic acid cycle. In particular,incorporation into protein and carbohydrate is much faster inacetate-grown cells and it is suggested that enzymes catalysingreactions leading away from the tricarboxylic acid cycle mayincrease in activity in acetate-grown cells. Light greatly stimulates acetate incorporation into lipide andalso increases the synthesis of protein and carbohydrate. 相似文献
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Nitrate refeeding of nitrogen-starved cells of Platymonas striataresulted in approximately a doubling of average cellular nitrogenwithin 24 h. All the nitrate-nitrogen removed from the culturemedium could be accounted for as non-nitrate nitrogen withincells. Thus no significantly sized nitrate pool existed in Platymonasstriata and no assimilated nitrogen was lost from the cellsto the medium over the 48 h period studied. The slight fallin average cellular nitrogen which occurred from 24 to 36 hcould be attributed to cell division. The majority (7080per cent) of the assimilated nitrate was recovered in the trichloroaceticacid (TCA)-insoluble fraction. There was some increase in thepercentage of nitrogen found in the TCA-soluble fraction duringthe period of most rapid nitrate assimilation (024 h).This presumably reflects an inability of the cells to assimilatelow-molecular-weight metabolic intermediates into macromoleculesat the same rate at which they were being formed. The majorityof the TCA-soluble fraction could be accounted for in termsof amino acids, purine and pyrimidine bases and ammonia. Cellswith adequate nitrogen nutrition seemed to maintain amino acidand purine + pyrimidine base nitrogen pools of about 0.80.9and 0.30.4 pg per average cell respectively. Algal amino acids, algal purine and pyrimidine bases, algal ammonia 相似文献
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Sterols of Chlorella. II. The Occurrence of an Unusual Sterol Mixture in Chlorella vulgaris 总被引:2,自引:2,他引:0 下载免费PDF全文
Patterson GW 《Plant physiology》1967,42(10):1457-1459
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The Effect of Cyanide on the Respiration and the Oxidative Assimilation of Glucose by Chlorella vulgaris 总被引:2,自引:0,他引:2
It is shown that low concentrations of cyanide stimulate theendogenous respiration of Chlorella vulgaris. When glucose isadded the respiration rate is much increased but is now reversiblyinhibited by cyanide. Some 3060 per cent. of the totalrespiration remains uninhibited. One-eighth to one-ninth ofthe glucose added is completely oxidized. Most of the remainderis assimilated to di- or polysaccharide. Low concentrationsof cyanide which inhibit the rate of glucose oxidation alsoinhibit the assimilation of glucose. Two possible interpretationsof this fact are discussed. It is suggested that the assimilationof glucose is coupled with the oxidation of glucose by a cyanide-sensitiverespiratory system. The mathematical consequences of this theoryare considered and shown to agree with the experimental results.The effect of cyanide on the respiratory quotient is also discussed. 相似文献
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Many microorganisms are capable of sequestering and concentrating heavy metals from their aqueous environment. While much research has beep carried out on the uptake of single species of metal ions, little attention seems to have been given to the study of multimetal ion systems. A mathematical model has previously been developed to describe the uptake of individual metal species by a microorganism. The model proposes two sequential processes: an initial rapid uptake due to cellular surface adsorption and a subsequent slow uptake due to membrane transport of the metal into the cells. This article extends the treatment by considering the uptake of two metal species together, cadmium and zinc, under different experimental conditions. The results are discussed in terms of possible mechanistic interactions. 相似文献
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Summary The excretion of glycolate by illuminated Chlorella vulgaris cells at low CO2 tension can be stimulated about tenfold by substituting O2 for air, or by addition of cyanide, hydroxylamine, hydrazine or semicarbazide to the cells in air. For each reagent there is a concentration range giving a maximum effect. It is proposed, as a working hypothesis, that the HCN formed internally when the cells are illuminated in O2, may cause the glycolate excretion. 相似文献
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Urea metabolism was studied with nitrogen-starved cells of Chlorella vulgaris Beijerinck var. viridis (Chodat), a green alga which apparently lacks urease. Incorporation of radioactivity from urea-(14)C into the alcohol-soluble fraction was virtually eliminated in cell suspensions flushed with 10% CO(2) in air. This same result was obtained when expected acceptors of urea carbon were replenished by adding ornithine and glucose with the urea. Several carbamyl compounds, which might be early products of urea metabolism and a source of the (14)CO(2), were not appreciably labeled. If cells were treated with cyanide at a concentration which inhibited ammonia uptake completely and urea uptake only slightly, more than half of the urea nitrogen taken up was found in the medium as ammonia. Cells under nitrogen gas in the dark were unable to take up urea or ammonia, but the normal rate of uptake was resumed in light. Since 3-(3,4-dichlorophenyl)-1,1-dimethylurea did not selectively inhibit this uptake, an active respiration supported by light-dependent oxygen evolution in these cells was ruled out. A tentative scheme for urea metabolism is proposed to consist of an initial energy-dependent splitting of urea into carbon dioxide and ammonia. This reaction in Chlorella is thought to differ from a typical urease-catalyzed reaction by the apparent requirement of a high energy compound, possibly adenosine triphosphate. 相似文献