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.     

The Effect of Manganese on the Assimilation and Respiration Rate of Isolated Rooted Leaves

The effect of manganese on carbon assimilation, respiration,and translocation has been studied using isolated rooted potatoleaves and small potato plants. Methods are described for therooting and culture of the leaves and plants. It was found thatnormal potato leaves rooted readily when treated with -naphtha-leneaceticacid (2 p.p.m.), but that very few of the manganese-deficientleaves produced roots, the critical level being about 15 p.p.m.manganese on a dry weight basis. The growth of isolated deficientleaves was also much less than that of control leaves, but inno case did characteristic manganese-deficiency symptoms develop,although the manganese level had fallen below that of leaveswhich showed symptoms when attached to the plant. A marked differencein net assimilation rate was found between leaves which hada high or low manganese content at the time of rooting. Theaddition of manganese after rooting to low manganese leavesdid not, however, cause an increase in assimilation rate, althoughthe manganese content of the leaves had been raised to thatof the control leaves. Manganese was shown to have only a smalleffect on respiration, higher respiration rate being consistentlyassociated with a higher manganese content; the addition ofmanganese to ‘deficient’ leaves did not cause anyincrease in respiration. No effect of manganese on translocationwas detected.     

Regulation of Nitrate Assimilation and Nitrate Respiration in Aerobacter aerogenes

The influence of growth conditions on assimilatory and respiratory nitrate reduction in Aerobacter aerogenes was studied. The level of nitrate reductase activity in cells, growing in minimal medium with nitrate as the sole nitrogen source, was much lower under aerobic than anaerobic conditions. Further, the enzyme of the aerobic cultures was very sensitive to sonic disintegration, as distinct from the enzyme of anaerobic cultures. When a culture of A. aerogenes was shifted from anaerobic growth in minimal medium with nitrate and NH(4) (+) to aerobiosis in the same medium, but without NH(4) (+), the production of nitrite stopped instantaneously and the total activity of nitrate reductase decreased sharply. Moreover, there was a lag in growth of about 3 hr after such a shift. After resumption of growth, the total enzymatic activity increased again slowly and simultaneously became gradually sensitive to sonic disintegration. These findings show that oxygen inactivates the anaerobic nitrate reductase and represses its further formation; only after a de novo synthesis of nitrate reductase with an assimilatory function will growth be resumed. The enzyme in aerobic cultures was not significantly inactivated by air, only by pure oxygen. The formation of the assimilatory enzyme complex was repressed, however, by NH(4) (+), under both aerobic and anaerobic conditions. The results indicate that the formation of the assimilatory enzyme complex and that of the respiratory enzyme complex are regulated differently. We suggest that both complexes have a different composition, but that the nitrate reductase in both cases is the same protein.     

Action of Patulin on a Yeast

The action of patulin on Saccharomyces cerevisiae was studied. At weak doses, the drug inhibited growth, but inhibition was transient. After 10 min, syntheses of rRNA, tRNA, and probably mRNA were blocked; this was shown by radioactive precursor incorporation assays and gel electrophoresis of RNAs. After recovery of growth, patulin disappeared from the medium. It seemed that this degradation resulted from the activity of an inducible enzymatic system. Induced cells resisted very high patulin concentrations.     

The Assimilation of Ammonia by Nitrogen-starved Cells of Chlorella vulgaris: Part I. The Correlation of Assimilation with Respiration

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 of0•75 compared with 1•2–1•3 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.     

Cyanide Insensitive Respiration of Sporobolomyces Red Yeast

The respiration of a Sporobolomyces red yeast is investigated with intact cells. The results show that the respiration is not inhibited at all, but moderately accelerated by cyanide and CO. Although the chemical nature of this fact is not yet clarified, the existence of a heat-labile and cyanide-insensitive oxidative enzyme system in this yeast is presumable.     

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.     

Draft Genome Assembly and Annotation for Cutaneotrichosporon dermatis NICC30027, an Oleaginous Yeast Capable of Simultaneous Glucose and Xylose Assimilation

The identification of oleaginous yeast species capable of simultaneously utilizing xylose and glucose as substrates to generate value-added biological products is an area of key economic interest. We have previously demonstrated that the Cutaneotrichosporon dermatis NICC30027 yeast strain is capable of simultaneously assimilating both xylose and glucose, resulting in considerable lipid accumulation. However, as no high-quality genome sequencing data or associated annotations for this strain are available at present, it remains challenging to study the metabolic mechanisms underlying this phenotype. Herein, we report a 39,305,439 bp draft genome assembly for C. dermatis NICC30027 comprised of 37 scaffolds, with 60.15% GC content. Within this genome, we identified 524 tRNAs, 142 sRNAs, 53 miRNAs, 28 snRNAs, and eight rRNA clusters. Moreover, repeat sequences totaling 1,032,129 bp in length were identified (2.63% of the genome), as were 14,238 unigenes that were 1,789.35 bp in length on average (64.82% of the genome). The NCBI non-redundant protein sequences (NR) database was employed to successfully annotate 11,795 of these unigenes, while 3,621 and 11,902 were annotated with the Swiss-Prot and TrEMBL databases, respectively. Unigenes were additionally subjected to pathway enrichment analyses using the Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), Cluster of Orthologous Groups of proteins (COG), Clusters of orthologous groups for eukaryotic complete genomes (KOG), and Non-supervised Orthologous Groups (eggNOG) databases. Together, these results provide a foundation for future studies aimed at clarifying the mechanistic basis for the ability of C. dermatis NICC30027 to simultaneously utilize glucose and xylose to synthesize lipids.     

Glucose Respiration in Zygorhyncus moelleri; the Entry of Glucose into the Cells

When glucose was added to carbohydrate-starved cells of Zygorhyncus,moelleri the rate of oxygen uptake did not immediately riseto a constant value, but there was a lag period of 2 or 3 hoursbefore it reached its maximum level. The length of this lagperiod increased from a few minutes for short periods of starvationto 2–3 hours after 12 hours in a carbohydrate-free medium.Factors believed to affect cellular permeability (a cationicdetergent, adjustments of the pH, and of the potassium/calciumratio) reduced the length of the lag period by not more than40 per cent. of the original value without affecting the finalrate of oxygen uptake. Investigation of the entry of glucoseinto the cells showed that the rate of oxygen uptake was notlimited by the concentration of intra-cellular glucose for morethat about 11 per cent. of the lag period in starved cells.The reasons for this difference in the percentage of the lagperiod apparently due to a permeability barrier are tentativelydiscussed in connexion with the route by which glucose entersthe cells.     

The Mode of Action of Toxic Protein in Wheat and Barley on Brewing Yeast

The mode of action of the toxic protein isolated from wheat on brewing yeast was investigated, and the following results were obtained: (1) The toxin inhibits respiration and fermentation of the yeast, and causes death of the cell in a few min (6 min) at a concentration of 4 ppm. (2) At a lower concentration (0.4 ppm), the toxin inhibits incorporation of sugars without causing death of the cells. (3) Potassium ion, phosphate ion, protein and nucleotides leak from the cell upon treatment with toxin at a lower concentration (0.4 ppm). (4) A directly proportional relationship exists between the lowest lethal concentration of the toxin and the yeast cell population. (5) The toxin is adsorbed onto the cell wall and cell membrane.

According to these results, the toxin seems to react with functional site(s) of the cell membrane causing changes in the permeability of the membrane and resulting in cell death.     

Glucose Respiration in the Intact Chloroplast of Chlamydomonas reinhardtii

Chloroplastic respiration was monitored by measuring ¹⁴CO₂ from ¹⁴C glucose in the darkened Chlamydomonas reinhardtii F-60 chloroplast. The patterns of ¹⁴CO₂ evolution from labeled glucose in the absence and presence of the inhibitors iodoacetamide, glycolate-2-phosphate, and phosphoenolpyruvate were those expected from the oxidative pentose phosphate cycle and glycolysis. The K_m for glucose was 56 micromolar and for MgATP was 200 micromolar. Release of ¹⁴CO₂ was inhibited by phloretin and inorganic phosphate. Comparing the inhibition of CO₂ evolution generated by pH 7.5 with respect to pH 8.2 (optimum) in chloroplasts given C-1, C-2, and C-6 labeled glucose indicated that a suboptimum pH affects the recycling of the pentose phosphate intermediates to a greater extent than CO₂ evolution from C-1 of glucose. Respiratory inhibition by pH 7.5 in the darkened chloroplast was alleviated by NH₄Cl and KCl (stromal alkalating agents), iodoacetamide (an inhibitor of glyceraldehyde 3-phosphate dehydrogenase), or phosphoenolpyruvate (an inhibitor of phosphofructokinase). It is concluded that the site which primarily mediates respiration in the darkened Chlamydomonas chloroplast is the fructose-1,6-bisphosphatase/phosphofructokinase junction. The respiratory pathways described here can account for the total oxidation of a hexose to CO₂ and for interactions between carbohydrate metabolism and the oxyhydrogen reaction in algal cells adapted to a hydrogen metabolism.     

The Inhibitory Action of Cycloheximide on Respiration of Coleoptiles is Relieved by Light

Concentrations of cycloheximide which are frequently used for the specific purpose of inhibiting protein synthesis also reduce oxygen uptake in Triticum and Avena coleoptiles in darkness by up to 50%. Except at high concentrations of the chemical diffuse daylight almost completely relieves this inhibitory effect provided the coleoptiles are not submerged. In darkness oxygen consumption is rapidly affected when cycloheximide is supplied to coleoptiles; the relief by light is also fast. These observations raise questions concerning the use of cycloheximide in studies with coleoptiles.