Energy-dependent transport of manganese into yeast cells and distribution of accumulated ions.

Manganese transport into yeast cells is energy-dependent. It is dependent on endogenous sources of energy and is inhibited by olygomycin (12.5-25 microgramg/ml), 2,4-dinitrophenol (1 mM), 2-deoxyglucose (1-50 mM) and sodium azide (1-10 mM), but is stimulated by cyanide and glucose. The stimulating effect of glucose is eliminated by N-ethylmaleimide and iodoacetate, which apparently inhibit the transport of glucose itself. About 75% of the manganese accumulated in the presence of glucose is found in yeast protoplasts and nearly 25% in the cell walls. A major portion of the accumulated manganese is found in vacuoles. The concentration of osmotically free manganese in the cytosol did not exceed 2 mM, but the concentration in vacuoles was up to 14 mM. The tonoplast is assumed to have a transport system for divalent cations, thereby regulating their concentration in the cytosol.     

Ability of yeast mitochondria to transport magnesium ions

Endomyces magnusii mitochondria were shown to be incapable of active Mg2+ transport at 0.1--16 mM concentrations. As was found using the inhibition analysis, when magnesium ions are added to the mitochondria once the phosphorylation cycle is over, the respiration is stimulated because adenylate kinase and H+-ATPase (Mg2+-dependent enzymes) are activated.     

Trehalose transport in yeast cells.

Saccharomyces cerevisiae possesses a specific transporter for trehalose. Transport is low until after glucose exhaustion in stationary phase, and addition of glucose in stationary phase results in loss of transport, an event that is reversible when the glucose is removed. The effect of glucose is not competitive inhibition: the increase in trehalose transport in stationary phase requires a lag time after glucose is depleted; and recovery of transport after glucose inhibition requires protein synthesis. Finally, we provide evidence that the trehalose transporter is distinct from that for maltose.     

The change in the electro-rotation of yeast cells effected by silver ions

Pre-treatment of brewer's yeast (Saccharomyces cerevisiae) cells with silver acetate or nitrate at concentrations of 20 nmol/l or higher caused a dramatic increase in the number of cells which rotated in the same direction as the field (‘Co-field rotation’). The change in rotation of single cells correlated very well with the chemically observed loss of potassium induced by Ag⁺. The sensitivity to Ag⁺ was lowered by increasing the cell concentration, and the extent of this change can be used to estimate the binding of Ag⁺ per cell and the limiting sensitivity of the method. The Ag⁺ concentration required to induce a response was found to be increased significantly in the presence of alkali ions (especially K⁺) during the Ag⁺ incubation. The Ag⁺ sensitivity was, therefore, observed to be a function of the type and strength of buffer used in the incubation. Under certain conditions, 1 mM Ca²⁺ increased the Ag⁺ sensitivity. These observations show that the presence or absence of ions that are so common that they are often overlooked may have interesting consequences for the bio-assay of heavy metals.     

The influence of the transpiration rate on uptake and transport of potassium ions in barley plants

Summary The vegetation points of branches of Caralluma frerei (Asclepiadaceae) were treated with 300, 100 and 30 ppm of crude aflatoxin (36% B₁, 38% G₁, 3% B₂, 2% G₂) and with toxin-free control. Application of 300 and 100 ppm aflatoxin resulted in stop of growth and death of the upper leaves and flower buds. Malformations or wilting was not observed in any case. Branches treated with 30 ppm aflatoxin and with control solution developed normally. It is concluced that under the experimental conditions used aflatoxin has an unspecific toxic effect.     

The influence of magnesium ions on pyruvate kinase-deficient red blood cells.

The effect of intravenous and oral administration of magnesium containing drug (Magnesium Diasporal, Protina, München) on the erythrocyte pyruvate kinase (PK) activity in two cases of congenital nonspherocytic hemolytic anemia associated with PK deficiency has been examined. Intravenous injection of the drug has been followed by transient increase in magnesium content. Positive correlation between erythrocyte magnesium ions concentration and PK activity has been found. The authors propose a hypothesis that the observed correlation may be due to the erythrocyte accumulation of some PK activators or to the elimination of some PK inhibitors. The authors did not, however, succeed to maintain the high erythrocyte magnesium concentration inducing the increase in PK activity during the longer period of time.     

Interactions between potassium ions and glycine transport in the yeast Saccharomyces carlsbergensis

A study has been made of the effects of both varying the pH and extracellular [K(+)] on the initial rate of uptake of glycine (v) by a strain of Saccharomyces carlsbergensis that concentrated the amino acid, with respect to the extracellular phase, by up to 1400 times. When no other substrate than glycine was provided and [glycine] was relatively small (相似文献   

Adsorption of metal ions on yeast cells at varied cell concentrations

Adsorption isotherms for adsorption of metal ions on yeast cellswere determined at varied cell concentrations. The mass of adsorbedmetal per unit weight of the cells at an equilibrium metal concentrationwas largely dependent on the cell concentration. An experimentalequation was presented, relating the included parameters. (Received August 19, 1975; )     

The participation of phosphate in the formation of a carrier for the transport of Mg++ and Mn++ ions into yeast cells

During the absorption of phosphate by yeast, the cells acquire the capacity to absorb Mn⁺⁺ and Mg⁺⁺, a capacity which is retained even after phosphate is no longer present in the medium. Cells pretreated with phosphate and then washed, slowly lose their ability to absorb Mn⁺⁺, the rate of loss depending on the temperature and on the metabolic state. The fermentation of sugars induces a very rapid loss of absorptive capacity, whereas the respiration of ethyl alcohol, lactate, or pyruvate has little effect. Inhibitor studies with sodium acetate, redox dyes, and arsenate, reveal parallel effects on Mn⁺⁺ absorption, and on phosphate absorption. It is concluded that the synthesis of a carrier for the transport of Mg⁺⁺ and Mn⁺⁺ involves a phosphorylation step closely coupled with reactions involved in the absorption of phosphate.     

The influence of yeast metabolism on dispersion in a fluidised yeast bed

Summary The effect of yeast metabolism on the dispersion characteristics of a fluidised bed fermentor containing flocs of the yeast Saccharomyces carlsbergensis was investigated. Dispersion in the metabolizing fluidised yeast floc system was compared with the dispersion in an inert yeast floc system and in a glass bead system. Breakdown in plug-flow was found to occur in the metabolically active yeast bed when the flow rate was increased over a relatively narrow operating range (up to a dilution rate of 0.08 h^-1). The superficial liquid velocity at which perfect mixing was approximated was some 18 times greater in the inert yeast floc system than in the metabolizing yeast floc system.Abbreviations C Tracer concentration - C ₀ Concentration of tracer at time t=0 - V Mixing chamber volume - v Volumetric flow rate - l Time - t Mean residence time - N Number of tanks in series - D/l Dispersion number - ² variance