Showing papers on "Yeast published in 1968"

The isolation, genetics and survival characteristics of ultraviolet light-sensitive mutants in yeast

Abstract: 96 mutants of yeast have been isolated which were more sensitive than wild-type to ultraviolet irradiation. Genetic analysis showed that many are inherited as single mendelian recessive mutations, and that they occupy at lest 22 different loci. Survival curves show that in all the mutants the low UV-dose shoulder characteristic of the survival curve of wild-type yeast is absent or very reduced, but that the slopes vary from one mutant to the next and are often complex. 5 mutants are also more sensitive to ionising radiation than wild-type and 5 reduce the ability of yeast to sporulate.

Studies on the nature of the killer factor produced by Saccharomyces cerevisiae.

Abstract: SUMMARY: Killer strains of yeast, Saccharomyces cerevisiae, liberate a killer factor into the medium which kills senstive yeast strains. The growth conditions necessary for the production of stable high-titre killer solutions and a biological assay for the killer factor are described. Purification was achieved by fractional precipitation with (NH4)2SO4, dialysis, gel filtration and ultrafiltration. The fractionated killer factor is an unstable macromolecular protein which is inactivated by papain. The death of sensitive cells is not coincident with absorption of the killer factor, but can be delayed or prevented by variations in the environmental conditions. Sensitive cells are most susceptible to the action of the killer factor when in log phase. Treated resting cells on entering log phase are killed immediately.

Glycerol metabolism in yeasts. Pathways of utilization and production.

Abstract: The utilization of glycerol by Candida utilis has been studied It has been found that this yeast has a permeability for glycerol and other three carbon compounds much greater than that of baker's yeast This permeability allows the entrance of glycerol in Candida cells rapidly enough to permit its efficient utilization even at low concentrations The inducibility of glycerol kinase has been established An increase in the concentration of the mitochondrial L-α-glycerophosphate oxidase when the yeast is grown on glycerol has also been observed A model is presented for the substrate specificity pattern of glycerol kinase of C mycoderma It postulates the involvement of three hydroxyl groups in the spatial distribution corresponding to the formation of L-α-glycerophosphate from glycerol This requirement can be met by aldo-and ketotrioses in their respective hydrated forms The pathway of glycerol formation in S cerevisiae has also been studied Evidence is shown of the existence of a NADH dependent enzymatic activity reducing triose phosphate to α-glycerophosphate which can roughly account for the glycerol production A low ionic strength seems to be required for the activity of this enzyme The α-glycerophosphatase is specific for the L from, the efficiency of α-glycerophosphatase on D-α-glycerophosphate being 1/30 of that on L-α-glycerophosphate The concentration of the α-glycerophosphatase in yeasts is higher when grown on hexoses than when grown on non-sugar carbon sources

THE BIOGENESIS OF MITOCHONDRIA : II. The Influence of Medium Composition on the Cytology of Anaerobically Grown Saccharomyces cerevisiae

Abstract: Yeast cells grown anaerobically have been shown to vary in their ultrastructure and absorption spectrum depending upon the composition of the growth medium. The changes observed in the anaerobically grown cells are governed by the availability of unsaturated fatty acids and ergosterol and a catabolite or glucose repression. All the cells contain nuclear and plasma membranes, but the extent of the occurrence of vacuolar and mitochondrial membranes varies greatly with the growth conditions. Cells grown anaerobically on the least nutritive medium, composed of 0.5% Difco yeast extract-5% glucose-inorganic salts (YE-G), appear to contain little vacuolar membrane and no clearly recognizable mitochondrial profiles. Cells grown anaerobically on the YE-G medium supplemented with Tween 80 and ergosterol contain clearly recognizable vacuolar membrane and some mitochondrial profiles, albeit rather poorly defined. Cells grown on YE-G medium supplemented only with Tween 80 are characterized by the presence of large amounts of cytoplasmic membrane in addition to vacuolar membrane and perhaps some primitive mitochondrial profiles. When galactose replaces glucose as the major carbon source in the medium, the mitochondrial profiles within the cytoplasm become more clearly recognizable and their number increases. In aerobically grown cells, the catabolite repression also operates to reduce the total number of mitochondrial profiles. The possibility is discussed that cells grown anaerobically on the YE-G medium may not contain mitochondrial membrane and, therefore, that such cells, on aeration, form mitochondrial membrane from nonmitochondrial sources. A wide variety of absorption compounds is observed in anaerobically grown cells which do not correspond to any of the classical aerobic yeast cytochromes. The number and relative proportions of these anaerobic compounds depend upon the composition of the growth medium, the most complex spectrum being found in cells grown in the absence of lipid supplements.

Specificity of the Constitutive Hexose Transport in Yeast

Abstract: A method has been developed based on the osmotic sensitivity of protoplasts, that permits turbidimetrical estimation of the penetration of non-metabolizable compounds into yeast protoplasts. Using this method a wide variety of sugars and related compounds have been tested as presumptive substrates for the constitutive hexose transport system in baker's yeast. An integration of the results obtained by this method with those obtained by other approaches has led to the establishment of the structural requirements that a compound has to meet in order to be transported. The basic structural requirement seems to be met by a pyranose ring for glucose and a furanose ring for fructose. With compounds that can be regarded as structurally related to d-glucopyranose, there is a broad tolerance for modifications at carbons 1 and 2, and somewhat less so for modifications at carbon 3. Similar requirements, except for carbon 2, apply to compounds that can be regarded as structurally related to D-fructofuranose. Physical diffusion of sugars, and related compounds, through the cell membrane of baker's yeast is very low, so that they only can enter into the cell at measurable rates by means of specific transport devices. The factor by which the entrance of glucose is increased over its physical diffusion, at concentrations in the millimolar range, is of the order of 106.

Control of dimorphism in Mucor by hexoses: inhibition of hyphal morphogenesis.

Abstract: In anaerobic cultures of Mucor rouxii, morphogenesis was strongly dependent on hexose concentration as well as pCO2. At low levels of hexose or CO2, or both, hyphal development occurred; at high levels, the fungus developed as yeast cells. Other dimorphic strains of Mucor responded similarly to hexose and CO2 but differred in their relative sensitivity to these agents. Glucose was the most effective hexose in eliciting yeast development of M. rouxii; fructose and mannose were next; and galactose was last. The fungus may be grown into shapes covering its entire dimorphic spectrum simply by manipulating the hexose concentration of the medium. Thus, at 0.01% glucose, hyphae were exceedingly long and narrow; at higher sugar concentrations, the hyphae became progressively shorter and wider; finally, at about 8% glucose, almost all cells and their progeny were isodiametric (spherical budding cells). Such yeast development occurred without a manifested requirement for exogenous CO2. The stimulation of yeast development by hexose is not an artifact due to increased production of metabolic CO2 (hyphae or yeast cells released metabolic CO2 at similar rates). Presumably, the effect was caused by some other hexose catabolite which interfered with hyphal morphogenesis (apical growth); deprived of its polarity, the fungus grew into spherical yeastlike shapes. Although 10% glucose inhibited the development of hyphae from germinating spores, it did not prevent the elongation of preformed hyphae. This suggests that hexose inhibits hyphal morphogenesis not by blocking the operation of the enzyme complex responsible for apical growth but by preventing its initiation; such inhibition may be regarded as a repression of hyphal morphogenesis.

Sulfur-Containing Nucleoside from Yeast Transfer Ribonucleic Acid: 2-Thio-5(or 6)-uridine Acetic Acid Methyl Ester

Abstract: A nucleoside, isolated from yeast transfer RNA, has been assigned the structure 2-thio-5-uridine acetic acid methyl ester on the basis of high-esolution mass spectrometry, chemical properties, and ultraviolet spectra. The alternate 6-substituted isomeric structure cannot yet be completely ruled out.

Induction and repression of mitochondrial ATPase in yeast.

Abstract: 1 A simple mechanical procedure for the preparation of particle-bound Mg-ATPase is described. It represented at least 80% of total ATPase activity, both in the case of aerobically and of anaerobically grown yeast. When analyzed in a sucrose gradient, ATPase from aerobic yeast sedimented with NADH-oxidase. ATPase from aerobic or anaerobic yeast showed 2 pH optima, as had been described for ATPase localized in carefully prepared and purified yeast mitochondria. Particle-bound ATPase from aerobic or anaerobic yeast showed pronounced oligomycin sensitivity. 2 Anaerobically grown yeast synthesized particle-bound Mg-ATPase at the low basal rate of 7–10 μmoles P/10 min/mg protein. During O2-induction without growth, respiratory enzymes and ATPase were induced simultaneously. Both inductions were inhibited by acti-dione. 3 Aerobically grown, glucose-repressed yeast synthesized ATPase at a rate similar to anaerobic yeast. Progressive derepression during growth produced a simultaneous increase of the rate of cell respiration (30–270) and of ATPase activity (10–60). 4 Ethanol-grown cells had a constant high Qo2 and synthesized ATPase at the high constant rate of 60. 5 Regulation of ATPase synthesis was strictly identical when activity was measured at the two pH optima, suggesting the presence of a single mitochondrial ATPase. The possibility of separate phosphorylating and hydrolytic sites on the enzyme is discussed.

Exo-β-glucanases in yeast

Abstract: 1. A number of yeast species were examined for the presence of β-glucanases. Extracts obtained by cell disruption of Saccharomyces cerevisiae, Fabospora fragilis and Hansenula anomala hydrolysed laminarin and pustulan with the production of glucose. Enzymic activities were also detected in the culture fluids of F. fragilis and H. anomala grown aerobically in buffered mineral medium with glucose as the carbon source. 2. F. fragilis and H. anomala possessed approximately sevenfold higher β-(1→3)-glucanase activity than S. cerevisiae . 3. Intracellular exo-β-glucanase from baker9s yeast was purified 344-fold from the dialysed cell extract. 4. Exo-β-glucanase from F. fragilis was purified 114-fold from the dialysed culture fluid and 423-fold from the dialysed intracellular extract. The purified extracellular and intracellular enzymes had similar properties and essentially the same specific activity, 79 enzyme units/mg. of protein. 5. Extracellular exo-β-glucanase of H. anomala was purified 600-fold. 6. The optimum pH of the enzymes from F. fragilis, S. cerevisiae and H. anomala was 5·5 in each case. Chromatographic evidence indicated that the three enzymes remove glucosyl units sequentially from laminarin as well as pustulan. 7. The ratio of activities towards laminarin and pustulan remained constant during purification of the exo-β-glucanase obtained from the three species, suggesting a single enzyme. Additional evidence for its unienzymic nature are: (i) the two activities were destroyed at exactly the same rate on heating of the purified enzyme from F. fragilis at three different temperatures; (ii) the competitive inhibitor glucono-δ-lactone gave the same value of K i when tested with either substrate; (iii) quantitative application of the ‘mixed-substrate’ method with the purified enzyme of S. cerevisiae gave data that were in excellent agreement with those calculated on the assumption of a single enzyme. 8. The purified exo-β-glucanases of the different species of yeast had different kinetic constants. The ratios of maximal velocities and K m values with laminarin and pustulan differed markedly. Comparison of V max. and K m values suggests that the rapid release of spores from asci in F. fragilis might be explained in terms of an enzyme with higher maximal velocity and higher affinity to the ascus wall than that present in baker9s yeast. 9. The estimated molecular weights for exo-β-glucanases from F. fragilis, S. cerevisiae and H. anomala were 22000, 40000 and 30000 respectively.

Multiple forms and subunits of yeast hexokinase.

Abstract: In a previous symposium of this Academy on multiple molecular forms of enzymes, a paper from this laboratory was presented (Kaji et al., 1961), in which multiple forms of yeast hexokinase were described. Since that time, it has been found that most, if not all, of these forms were derived by the action of a protease acting during the course of the preparation. In the present paper, the nature of this modification process is described, and the chemical, physical, and catalytic properties of unmodified and modified enzyme are summarized. Evidence is presented that, when proteolytic modification is avoided, two distinct forms of yeast hexokinase can be demonstrated, with different catalytic and chemical properties. The method for preparing these unmodified forms has been described elsewhere (Schulze et al., 1967). Similar results have been obthined independently in Barnard's laboratory (Lazarus et al., 1966 and Derechin et al., 1966).

Production of d-Mannitol and Glycerol by Yeasts

Abstract: D-Mannitol has not so far been known as a major product of sugar metabolism by yeasts. Three yeast strains, a newly isolated yeast from soy-sauce mash, Torulopsis versatilis, and T. anomala, were found to be good mannitol producers. Under optimal conditions, the isolate produced mannitol at good yield of 30% of the sugar consumed. Glucose, fructose, mannose, galactose, maltose, glycerol, and xylitol were suitable substrates for mannitol formation. High concentrations of yeast extract, Casamino Acids, NaCl, and KCl in media affected significantly the mannitol yield, whereas high levels of inorganic phosphate did not show any detrimental effect.

Glucose induced inactivation of malate dehydrogenase in intact yeast cells.

Abstract: The glucose-dependent inactivation of malate dehydrogenase (l-malate: NAD oxidoreductase, EC 1.1.1.37) in acetate-grown yeast cells was studied in vivo. Among different yeast species inactivation was observed only in strains of the genus Saccharomyces. The phenomenon is initiated by the addition of glucose or related hexoses to the medium and is reversibly interrupted at 0°. By use of a yeast mutant requiring tryptophan, it was shown that malate dehydrogenase inactivation is not influenced by inhibition of protein synthesis, whereas recovery of enzyme activity in inactivated cells requires the presence of an energy source and tryptophan and is presumably due to de novo protein synthesis. The reported results provide evidence that a metabolite formed in the first steps of glycolysis might be responsible for initiation of malate dehydrogenase inactivation.

Molecular aspects of specific cell contact.

Abstract: Complementary macromolecules were isolated from yeasts of opposite mating type. These cell-surface molecules neutralize each other as do antibodies and antigens. Both yeast factors are glycoproteins of low molecular weight. Other specific cell associations may be due to the interaction of such complementary macromolecules.

Yeast growth and glycerol formation ii. carbon and redox balances

Abstract: Compared to alcoholic fermentation, the biosynthesis of a yeast cell is an oxidation process. To maintain the redox balance, this oxidation is counterbalanced by reduction of dihydroxyacetone phosphate to glycerol. Many other substances affecting the redox balance of the yeast cell are also formed as by-products of alcoholic fermentation. Carbon and redox balances including thirteen substances are presented in this paper; they are in good agreement with the concept that the biosynthesis of I g. (dry matter) of yeast gives rise to the formation of about 6 mmoles of glycerol.

Budding of Yeast Cells, their Scars and Ageing

Abstract: Publisher Summary This chapter discusses results of direct observations on some structures of the cell surface of intact budding yeast cells in a fluorescence microscope with the results of other investigations. The fluorochrome primulin is used for distinguishing between viable and dead yeast cells. At higher concentrations, primulin makes it possible to observe directly the scars in all types of vegetative reproduction of yeast cells. It is also possible to define three new types of yeast cell walls by following the formation of structures by induced fluorescence during the course of reproduction, together with their submicroscopic structure in an electron microscope. Yeast cell wall is mostly composed of polysaccharides accompanied by some proteins, lipids, and glucosamine. The ratio of the various types of components varies from species to species. The main differences are observed in the amounts of mannans, lipids and glucosamine, particularly in the form of chitin. The scars on yeast cells reproduce in four different ways—namely, (1) multipolar budding, (2) bipolar budding, (3) division, and (4) terminal growth. The chapter describes composition and structure of the cell wall of yeast, mechanism of the primulin-induced fluorescence, budding of yeast cells and its mechanism, and ageing of cells and age distribution in a population.