The Disappearance of Intermediates involved in Glucose Oxidation during the Starvation of the Fungus Zygorhyncus moelleri

The respiration of carbohydrate-starved cells of Zygorhyncusmoelleri showed a lag period of 2 to 3 hours when glucose wasadded before the rate of oxygen consumption became constant.Analysis of the rates of oxygen uptake from the time of additionof the sugar until they became constant showed that the lagperiod could not be ascribed entirely to a low concentrationof free glucose in the cells in the period immediately followingthe addition of glucose to the medium. The analysis was, however,consistent with the supposition that the synthesis of an intermediarymetabolite on the glucose oxidation pathway was necessary beforethe oxidation could proceed with a maximum speed. The lengthof the lag period could be reduced by adding extracts of cellstogether with glucose; extracts of unstarved cells were moreeffective than those of starved cells in shortening the lagperiod. Various known substances were also effective in thisrespect, acetate and ethanol being the most active. These resultsare discussed together with earlier work on the lag period.     

Links between Glucose Uptake and Metabolism in Nitella translucens

The uptake of ¹⁴C-glucose into cells of Nitella translucenshas been investigated under experimental conditions previouslyused in studies of the ionic relations of these cells. Glucoseentry was considerably stimulated by light, and under aerobicconditions the fluxes remained constant for many hours. Theinflux of glucose was inhibited by over 80 per cent at low temperature(4° C) and by over 90 per cent by the uncoupler carbonylcycanide-m-chlorophenylhydrazone. 2-Deoxy-D-glucose was a non-competitiveinhibitor of glucose uptake both in light and darkness. Cyclicphotophosphorylation promoted the influx (with decreasing efficiency)for several hours. It is suggested that an ATP-dependent transportprocess controls glucose entry to the cells, and that passivediffusion is of little significance.     

The Action of Nitrophenols on Respiration and on Glucose Assimilation in Yeast

The consumption of 2·25 mg. glucose by a resting suspensionof baker's yeast in the presence of finely graded concentrationsof 3:5 -dinitro-o-cresol was followed at pH 2·4 and 5·0by measuring oxygen uptake and carbon-dioxide output; at pH8·5 oxygen uptake alone was measured. At each pH certainconcentrations of dinitrocresol stimulated respiration and increasedthe ratio of glucose oxidized to glucose assimilated; at higherconcentrations, assimilation was reduced to zero, but respirationbecame inhibited and the whole of the glucose was then metabolizedby aerobic fermentation. Dinitrocresol is believed to be actingin these experiments as an uncoupling agent, lowering the netrate of formation of energy-rich phosphate and so allowing respirationto proceed faster while assimilation, an endergonic process,is inhibited. The maximum respiratory stimulation obtainable at pH 8·5,325 per cent, of the control, is greater than can be obtainedat pH 2·6 or 5·0, which may be due to the slowerrespiration rate of controls at pH 8's. The slow endogenousrespiration can also be stimulated more than the exogenous.With o- and p-nitrophenols similar relations are obtained, butphenol does not stimulate respiration, although it inhibitsassimilation in lower concentrations than respiration. Undernitrogen, a stimulation of fermentation can be obtained withdinitrocresol at pH 5·0 but not at 2·6. At bothpH levels, assimilation is more easily suppressed than fermentationrate.     

Oxidative Assimilation of Glucose by Scenedesmus quadricauda

The utilization of glucose by Scenedesmus quadricauda has beenstudied by manometric methods. With small amounts the oxidationonly goes to about 16 per cent. of completion, the remainderof the glucose being built up into an acid-hydrolysable polysaccharidewhich is not starch, and which is built up from a hexose otherthan fructose. The extent of the oxidation is not affected by sodium azideor 2:4-dinitro-phenol, but can be varied by altering the pHof the suspension medium; more oxygen is absorbed per unit weightof glucose at pH 8 than at pH 5. It is suggested that there is no fixed relation between thetwo processes of oxidation and synthesis, as has previouslybeen suggested, but that the glucose, after phosphorylation,saturates the oxidation system, and the excess hexose-phosphateis built up into a polysaccharide. Mannose is also utilized in the same way, but at a slower rate,and less oxygen is used up compared with glucose. Galactosegives only a slight stimulation of the respiratory rate, andfructose, sucrose, and lactose are not absorbed.     

Studies on the Growth and Respiration of Roots: I. THE EFFECTS OF STIMULATORY AND INHIBITORY CONCENTRATIONS OF {beta}-INDOLYLACETIC ACID ON ROOT SECTIONS OF PISUM SATIVUM

Simultaneous observations on extension growth and respirationrate (oxygen consumption) of 2-mm. sections excised from theextension zone of roots of pea (Pisum sativum) growing in distilledwater and 0·5 per cent. sucrose have yielded resultsclosely similar to those of Brown and Sutcliffe (1950). Respirationrate is not obviously correlated with growth rate either inwater or in sucrose, but it is strongly correlated with sectionlength. Respiration rate per unit section length (¬per unitfresh weight) shows a marked downward drift during extensionand is affected little by growth conditions. Tentative suggestionsare advanced to account for the small differences between driftsin o·5 per cent. sucrose and those in distilled water. Medium agitation produces an immediate and sustained stimulationof growth but no stimulation of oxygen uptake until the latergrowth stages. Thus respiration per unit section length is unaffectedby agitation at any stage. A typical growth response to ß-indolylacetic acid(IAA) was obtained, with a maximum stimulation (of about 35per cent.) at 1 part in 10¹¹ and inhibitions increasing progressivelywith concentration beyond the threshold of about i part in 10⁹.Both percentage stimulation and percentage inhibition of growthwere independent of the presence of sucrose. Respiratory responses to ß-indolylacetic acid werecomplex. In water no immediate response could be detected witheither a growth-stimulatory (10^–11) or a growth-inhibitory(10^–-8) concentration, while in 0·5 per cent. sucrosethe inhibitory concentration prevented the small immediate respiratoryrise due to the sucrose, probably by impeding sugar entry. Duringthe subsequent period of rapid growth (up to 36 hours) the smallrespiratory responses observed closely followed the small growthresponses to both concentrations of IAA, suggesting that theformer are the direct result of the differences in section lengthinduced by the auxin. When growth ceases (at 48 hours) sectionswhich have grown considerably in sucrose show respiratory ratesstill closely correlated with section length, whereas in waterboth concentrations of auxin induce marked depressions in respirationrate. It is concluded that ß-indolylacetic acid in bothgrowth-stimulatory and growth- inhibitory concentrations hasno direct effect on the activity of the respiratory enzyme systemof growing root cells. The small respiratory responses are bestexplained as resulting from differential changes in sectionsize and correlated changes in the enzyme complements of thegrowing cell.     

The Influence of Gaseous Environment on the Storage Life of Araucaria hunsteinii Seed

The effect of various gas mixtures on the longevity of hydratedseeds of Araucaria hunsteinii K. Schum. was assessed under controlledconditions. The length of storage life decreased as oxygen concentrationwas reduced from 21 to zero per cent. No effect of carbon dioxideon seed longevity was detected within the range 1–50 percent when combined with 10 or 21 per cent oxygen. Ethylene at0.01 per cent, and sealed foil or polyethylene bag storage reducedthe period of seed germinability compared with that for 21 percent oxygen. Ethanol accumulation took place in stored seedswhen the environmental oxygen concentration was below a thresholdvalue which lay between 1 and 5 per cent. It is proposed that the observed effects of gases on longevityof hydrated seeds may be mediated through an influence on aerobicrespiration rate. Practical implications of the results areconsidered. Araucaria hunsteinii, Klinkii pine, seed longevity, seed storage, gas environments, oxygen, carbon dioxide, ethanol accumulation     

Wheat Viability at High Moisture Content under Hermetic and Aerobic Storage Conditions

Wheat seeds (Triticum durum) were stored under both hermeticand aerobic conditions at 25 °C with moisture contents from15 to 33 per cent. Under hermetic storage, seeds lost viabilitymore rapidly the higher the moisture content, whereas in aerobicstorage, seed longevity was enhanced as the moisture contentwas increased from 24 to 31 per cent, and over this range ofmoisture content the seeds survived longer under aerobic thanhermetic storage. On the contrary, an apparent reversal of thistrend occurred when moisture content was increased above 31per cent. The possibility that the changes in longevity occurring at highermoisture contents might be due to the activation of seed metabolismwas supported by the enhanced incorporation of [³H]leucine intoTCA insoluble material (indicating increased protein synthesis)and the reduced leakage of glucose (indicating increased membranerestitution) when seeds were allowed to achieve higher moisturecontents during the prehydration period. The highest level ofseed activation was found in seeds preconditioned to about 31per cent moisture content. Moreover, these seeds, when subsequentlystored under aerobic conditions, maintained a higher rate ofprotein synthesis and lower membrane permeability during thestorage period than seeds at lower water contents. It is suggested that seeds stored at a sufficient hydrationlevel in the presence of oxygen can sustain an effective metabolismduring extended storage, thus permitting the repair of cellulardamage. However, it might be possible that at about 33 per centmoisture content seed could suffer from an excessive advancementof metabolism. Triticum durum, seed storage, effects of high moisture content and oxygen     

Factors controlling the metabolic response to glucose in isolated rat lung cells

Glucose decreases the oxygen utilization by isolated rat lung cells. Its effect displays saturation type kinetics with a “Ki” of 2.2. mM. The similarity of this value with the reported “Km” of 2.4 mM described for glucose uptake by these cells, suggests that both processes may be intimately related and both of them are under the control of the same rate limiting step. Several arguments point to glucose transport into these cells as the most important rate limiting step for its utilization: 1) Phloridzin prevented glucose inhibition of oxygen uptake while mannoheptulose did not; 2) The activity of hexokinase which is the least active glycolytic enzyme in these cells far exceeded the observed rates of glucose utilization and a decrease of 45 per cent in its activity in starved animals did not affect the rate of glucose uptake; 3) The “Km” of hexokinase for glucose is two orders of magnitude below the observed “Km” for glucose uptake and the “Ki” for glucose inhibition of respiration.     

Diauxic Growth of Azotobacter vinelandii on Galactose and Glucose: Regulation of Glucose Transport by Another Hexose

The growth curve of Azotobacter vinelandii was biphasic when the organism was grown in a medium containing a mixture of galactose and glucose. Galactose was the primary carbon source; glucose was also consumed, but the rate at which it was consumed was lower than the rate at which galactose was consumed during the first phase of growth. Metabolic pathways for both sugars were induced. Cell cultures exhibited a second lag period as galactose was depleted. The length of this lag phase varied from 2 to 10 h depending on the pregrowth history of the cells. The second log growth phase occurred at the expense of the remaining glucose in the medium and was accompanied by induction of the high-maximum rate of metabolism glucose-induced glucose permease and increases in the levels of glucose metabolic enzymes. The second lag phase of diauxie may have been due to the time required for induction of the glucose-induced glucose permease.     

An Examination of the Factors affecting Variability in the Growth of the Mesocotyl and Coleoptile of Etiolated Avena Seedlings

Experiments were carried out on the effect of rate of air-flowand of humidity on the growth of Avena seedlings. The experimentalmethods used are described in some detail. The effect of air-flow on mesocoryl growth was considerablewhen unsaturated air was used, but with saturated air growthwas independent of air-flow. The effect must therefore be dueto variation in transpiration rate. A 10 per cent, variationin relative humidity, at a constant rate of flow, caused a 30per cent, variation in mesocotyl length. The coleoptiles showedless pronounced effects, but even in saturated air variabilitywas not eliminated. Under the conditions used a difference of 2·3 mm. inmesocotyl length (per 50 plants), i.e. 8 per cent., was significantat P = 0·05; for the coleoptiles a difference of 1 mm.(8 per cent.) was significant at this level.     

Increases in the number of adventitious roots caused by 2-thiouracil and 5-bromodeoxyuridine in Phaseolus mungo cuttings

A cutting of Phaseolus mungoproduced about 4 adventitious rootsat the basal 1 mm region when the basal part of the cuttingwas dipped in water. Rootlets became visible after a 36 hr lagperiod in untreated cuttings. Treatment with 2-thiouracil or5-bromodeoxyuridine increased the number of roots formed onthe cutting and prolonged the lag period. Effects of 2-thiouraciland 5-bromodeoxyuridine were reversed by simultaneously applieduracil and thymidine. The number of roots decreased and thelength of lag period was shortened. The increases in the numberof roots by 2-thiouracil or 5-bromodeoxyuridine was reducedby gibberellic acid, which did not cause a decrease in the numberof roots to be formed on control cuttings. Roots formed at thebasal region seem to suppress further root formation at theupper part of the hypocotyl. Inhibitors used here probably workby blocking the formation of these bottommost roots. (Received April 30, 1971; )     

The Effect of Cyanide on the Respiration and the Oxidative Assimilation of Glucose by Chlorella vulgaris

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 30–60 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.     

Studies on the Growth in Culture of Plant Cells: VII. EFFECTS OF KINETIN ON THE CARBOHYDRATE AND NITROGEN METABOLISM OF ACER PSEUDOPLATANUS, L CELLS GROWN IN SUSPENSION CULTURE

Aspects of the carbohydrate and nitrogen metabolism of Acerpseudcplatanus, L cell suspension cultures grown on a syntheticmedium containing 2 per cent glucose and 1.0 mg/l 2,4-dichlorophenoxyaceticacid and kinetin either at 0.25 mg/l (low kinetin) or at 2.5mg/l (high kinetin) are described. High kinetin inhibits growthas measured by increase in cell number, packed-cell volume,and cell dry weight. Although not inhibitory to glucose utdization,high kinetin inhibits the O₂ uptake of the cells. Such cellscontain only a trace amount of fructose and their rate of O₂uptake can be raised to that of the low kinetin cells by a periodof fructose feeding. The O₂ uptake of both kinds of cell issensitive to malonate but the stimulation of O₂ uptake inducedby bis(hexafiuoroacetonyl)-acetone (‘1799’) at 0.2mM is much less with the high-kinetin than the low-kinetin cells.The enzymes phosphoglucoseiseomerase and glucose-6-phosphatedehydrogenase are much less active in the high-kinetin cells.Mitochondria isolated from both kinds of cells show good respiratorycontrol although slightly lower values for Q_O2(N), ADP/O ratioand control ratio are recorded with mitochondria from the highkinetin cells. Kinetin at 2.5 mg/l slightly reduces the ADP/Oratio of isolated mitochondria but at 4.0 mg/l their responseto ADP is completely suppressed. Extracellular hemicelluloseformed in presence of high kinetin has a reduced content ofgalactose and xylose and an increased content of glucose. Theseobservations indicate that the inhibition of respiration byhigh kinetin is mainly due to suppression of glucose conversionto other sugars rather than to inhibition of glycolysis or terminalrespiration. High kinetin decreases the rate of protein but not of amino-acidsynthesis. Suppression of the synthesis of particular proteinsmay be an important factor responsible for the reduced cellyield of the cultures in presence of high kinetin. The significanceof these observations to our understanding of the critical metaboliceffects of cytokinina is discussed. Acer pseudoplatanus cells release amino acids into their culturemedium early in the period of batch culture and largely reabsorbthem as incubation proceeds.     

Glucose uptake by the cellulolytic ruminal anaerobe Bacteroides succinogenes.

Glucose uptake by Bacteroides succinogenes S85 was measured under conditions that maintained anaerobiosis and osmotic stability. Uptake was inhibited by compounds which interfere with electron transport systems, maintenance of proton or metal ion gradients, or ATP synthesis. The most potent inhibitors were proton and metal ionophores. Oxygen strongly inhibited glucose uptake. Na+ and Li+, but not K+, stimulated glucose uptake. A variety of sugars, including alpha-methylglucoside, did not inhibit glucose uptake. Only cellobiose and 2-deoxy-D-glucose were inhibitory, but neither behaved as a competitive inhibitor. Metabolism of both sugars appeared to be responsible for the inhibition. Cells grown in cellobiose medium transported glucose at one-half the rate of glucose-grown cells. Spheroplasts transported glucose as well as whole cells, indicating glucose uptake is not dependent on a periplasmic glucose-binding protein. Differences in glucose uptake patterns were detected in cells harvested during the transition from the lag to the log phase of growth compared with cells obtained during the log phase. These differences were not due to different mechanisms for glucose uptake in the cell types. Based on the results of this study, B. succinogenes contains a highly specific, active transport system for glucose. Evidence of a phosphoenolpyruvate-glucose phosphotransferase system was not found.     

Permeability of Whole Dunaliella Cells to Glucose

Ginzburg, M. and Richman, L. 1985. Permeability of whole Dunaliellacells to glucose.—J. exp. Bot. 36: 1959–1968.Whenglucose was dissolved in medium in which Dunaliella cells weresuspended, the amount recovered from pellets of centrifugedcells was greater than that expected if the glucose had beenrestricted to intercellular space, as measured with Blue Dextran.Glucose is not metabolized by whole Dunaliella cells. The glucoseadditional to that in the intercellular space must be eitheradsorbed in the coating outside the cells or must penetratethe cell through the cell membrane. Grounds are given for suggestingthat the latter hypothesis is correct and that the glucose comesto equilibrium with a space within the cell (the glucose–space)equivalent to 20–40% of the cell–water. It is suggestedthat most of the cell Na⁺ is restricted to the glucose-space. Key words: Dunaliella, glucose, permeability     

Glucose and Pyruvate Metabolism in Daucus carota Cells: The Effect of the Ammonium Ion

In Daucus carota cells cultivated in vitro, the ammonium ionstimulates the incorporation of radioactivity from labelledglucose and labelled pyruvate into CO₂ and into the residueinsoluble in 60 per cent (v/v) ethanol. There is a higher ¹⁴CO₂production from [6-¹⁴C₂] glucose than from [6-¹⁴C] glucose.These results suggest a possible stimulation of glycolysis bythe ammonium ion.     

Nitrogen Metabolism of Detached Kalanchoe Leaves in the Dark in Relation to Acidification, Deacidification, and Oxygen Uptake

Detached Kalancho leaves were placed in the dark and changesin the amounts of total soluble N, asparagine, glutamine, aminoN, ammonia, and titratable acid were followed during the periodsof acidification and deacidification. Abundant starch was presentthroughout the experiments. The amount of acid which accumulatedin the initial period was increased by placing the leaves in5 per cent. CO₂ and also by decreasing the temperature from25 to 10°. In neither case were the nitrogen fractions affectedin a similar way to the acid levels. No consistent relationshipcould be found between the amount or change in amount of acidand the amounts of the nitrogen fractions. Over prolonged periodsthe drifts in the amounts of the nitrogen fractions were verysimilar to those known in non-succulent leaves. It is concludedthat, despite the large amounts of free acid and starch present,the nitrogen metabolism of detached Kalancho leaves in the darkis similar to that of non-succulent leaves. A possible explanationis suggested for the incorporation of ¹⁴C from ¹⁴CO₂ into nitrogenoussubstances in Kalancho leaves during dark acidification. Changesin the amounts of glutamine, which seemed to be related to oxygenuptake rather than to acid fluctuations, were measured in comparableleaf samples showing different rates of oxygen uptake. The rateof oxygen uptake of leaves and leaf disks in the dark was controlledby placing them in an atmosphere of nitrogen, or 5, 20, or 100per cent, oxygen, by the addition of 10^–3 M. cyanide,or by varying the temperature. At the end of a given periodthe amount of glutamine was always greater in the samples whichhad shown the higher rate of oxygen uptake during this perod.This correlation was found irrespective of whether the amountof glutamine had increased or decreased. With the assumptionsthat glutamine production and consumption were proceeding simultaneouslyand that the rate of consumption was unaffected by the rateof oxygen uptake, the experimental values are consistent withthe hypothesis that the rate of glutamine production and therate of oxygen uptake were directly related. The possible significanceof these findings is discussed.     

Some Factors Which Affect Amino Acid Uptake by Saccharomyces carlsbergensis

When fully grown cells of Saccharomyces carlsbergensis were suspended in a solution of glucose and labeled amino acids, there was a lag phase before rapid uptake of certain amino acids. During this lag, significant amounts of sugar were utilized. The lag phase varied in length, depending upon the amino acid under study, but could be shortened by aeration of the cells and eliminated by their preincubation in glucose solution. Divalent metal ions, especially Ca²⁺ added during the early stages of the lag phase, increased the length of the lag, an effect that could be reversed by washing with ethylenediaminetetraacetate, but amino acids which normally showed little or no lag before uptake were insensitive to Ca²⁺. The rate of uptake of amino acids or of sugar was essentially unaffected by Ca²⁺, whereas 2,4-dinitrophenol caused an overall decrease in the rate of uptake of all amino acids tested. The relevance of these observations to commercial brewing practice is shown.     

Sporulation in Rhizopus sexualis and Some Other Fungi Following a Period of Intense Respiration

Rhizopus sexualis grown at 20° C. on liquid I per cent.malt or glucose-asparagine medium showed a peak of respiratoryactivity between 40 and 55 hours-after inoculation. Rate ofrespiration then fell until it reached a steady low level whichcoincided with maximum mycelial growth. Zygospore initiationoccurred at or just after the peak of respiration. At a low temperature (9° C.) or with high concentrationsof glucose the respiration peak was less marked and no zygosporesdeveloped. Single ‘plus’ or ‘minus’strains of the heterothallic species Mucor hiemalis and Phycomycesblakesleeanus showed a pattern of respiration and mycelial growthsimilar to that of R. sexualis but no zygospores were formed.Zygospores did not develop without a preliminary period of intenserespiration, but such a peak period could occur without beingfollowed by zygospore formation. A strain of Sordaria fimicola was grown at 25° C. on a syntheticmedium with 5.0 per cent. sucrose or glucose as source of carbon.Respiration reached a peak at approximately 4 and 5 days respectively,the actual peak value being twice as large on sucrose as onglucose. Dry weight of mycelium was greater on glucose thanon sucrose. Perithecia were formed only on the sucrose medium.Visible peri-thecial initials were first seen shortly afterthe occurrence of the respiratory peak. Mature perithecia werepresent 3 days later. The possible significance of these results is discussed.     

Growth of Sclerotiumrolfsiiat Different Concentration of Oxygen and Carbon Dioxide

Sclerotium rolfsii was grown in various atmospheres, the compositionsof which were controlled by the diffusion column technique.Growth-rate of mycelium was constant within a range of oxygenconcentrations from 3 to 21 per cent, but dirminished steadilyas carbon dioxide concentration increased from about 0.03 percent. The rate of sclerotial germination was reduced by oxygenconcentrations less than 6 per cent and by carbon dioxide concentrationsgreater than about 10 per cent. No sclerotia were formed ifthe concentration of oxygen fell below 15 per cent or if thatof carbon dioxide exceeded 4 per cent. The effects of inverserationof gases, from 0 per cent oxygen: 20 per cent carbon dioxideto 21 per cent oxygen: 0 per cent carbon dioxide, were in eachcase similar to the effect of the corresponding carbon dioxideconcentration when combined with 21 per cent oxygen.