Yeast membrane permeability

Catechins Yeasts Cell membrane Polyenes Stimulation membrane permeability increased intracellular catechin concentration [53]... 

Mecfianism of Action An antifungai that binds with phospholipids in fungal cell membrane. The altered cell membrane permeability. Therapeutic Effect Inhibits yeast growth. 

Physical and chemical genetic techniques have been used to enhance the permeability of yeast membranes. Permeabilizing agents, such as polymyxin B sulfate and polymyxin B nonapeptide, have been used to physically disrupt the integrity of yeast membranes (14). However, use of such chemical agents in drug screening is not ideal, because of the toxicity induced by polymyxin B treatment. 

An important harmful effect of metals at the cellular level is the alteration of the plasma membrane permeability, leading to leakage of ions like potassium and other solutes (Passow and Rothstein, 1960 Wainwright and Woolhouse, 1978 De Filippis, 1979 De Vos et al., 1988, 1991). After supply of copper ions Ohsumi et al. (1988) demonstrated for yeast cells and De Vos et al. (1989) for root cells of Silene cucubalus that the permeability barrier (controlled by means of potassium leakage) of the plasma membrane was almost immediately lost. Oshumi et al. (1988) also reported a quick release of amino acids, especially glutamate and aspartate. After McBrien and Hassall (1965) and Overnell (1975), who studied potassium release from algal cells, the increased permeability of the plasma membrane may be considered to constitute the primary toxic effect of copper. 

Clotrimazole and other azole derivatives have a different mode of action than the polyenes, eg, amphotericin B. The latter bind to the ergosterol present in the membranes of yeasts and fungi, but azole derivatives inhibit the cytochrome P-450 dependent biosynthesis of eigosterol (8—11). This inhibition not only results in a reduction of ergosterol, but also in an accumulation of C-14 methyl sterols. They disturb membrane permeability, inhibit cell replication, and are basically responsible, in combination with the reduction of ergosterol levels, for the antifungal action. 

The mechanism of action of these macrolide antibiotics is now known to affect membrane permeability of sensitive cells. These cells are almost exclusively eukaryotic and therefore do not include bacteria. Fungi, both dermatophytes and yeasts, and, unfortu-... 

Warth, A.D., Relationships among cell size, membrane permeability, and preservative resistance in yeast species, Appl., Environ. Microbiol., 55, 2995, 1989. 

The point at which the fungal cell can be considered dead is debatable [297]. It is not possible to reverse the lethal action of polyenes once sufflcient antibiotic molecules have combined with the cell membrane. Lethal levels of nystatin brought glycolysis of S. cerevisiae to a halt within 40 min [298] and 95% of the yeast cells were not viable after 30 min. Cell death inevitably follows destruction of membrane permeability. Whether the observed changes in cell metabolism, composition or morphology are causes or symptoms of death is unclear the sequence of antibiotic action in organisms other than fungi has received little attention. 

Research into the impact of various fermentation by-products on yeast demonstrated the inhibiting effect of Ce, Cg, and Cm short-chain fatty acids found in wine at concentrations of a few milligrams per liter. They affect cell membrane permeability and hinder exchanges between the inside of the cell and the fermenting medium. When fermentation stops, the yeast enzymatic systems still function, but the sugars can no longer penetrate the cell to be metabolized (Larue etal., 1982). Salmon et al. (1993) confirmed that loss of activity... 

Latoud, C., F. Peypoux, and G. Michel Action of Iturin A, an Antifungal Antibiotic from Bacillus subtilis, on the Yeast Saccharomyces cerevisiae Modifications of Membrane Permeability and Lipid Composition. J. Antibiotics 40, 1588 (1987). Latoud, C., F. Peypoux, and G. Michel Action of Iturin A on Membrane Vesicles from Saccharomyces cervisiae Activation of Phospholipases A and B Activities by Picomolar Amounts of Iturin A. J. Antibiotics 41, 1699 (1988). 

Electroporation. When bacteria are exposed to an electric field a number of physical and biochemical changes occur. The bacterial membrane becomes polarized at low electric field. When the membrane potential reaches a critical value of 200—300 mV, areas of reversible local disorganization and transient breakdown occur resulting in a permeable membrane. This results in both molecular influx and efflux. The nature of the membrane disturbance is not clearly understood but bacteria, yeast, and fungi are capable of DNA uptake (see Yeasts). This method, called electroporation, has been used to transform a variety of bacterial and yeast strains that are recalcitrant to other methods (2). Apparatus for electroporation is commercially available, and constant improvements in the design are being made. 

In Saccharomyces cerevisiae, as in most eukaryotic cells, the plasma membrane is not freely permeable to nitrogenous compounds such as amino acids. Therefore, the first step in their utilization is their catalyzed transport across the plasma membrane. Most of the transported amino acids are accumulated inside the yeast cells against a concentration gradient. When amino acids are to be used as a general source of nitrogen, this concentration is crucial because most enzymes which catalyze the first step of catabolic pathways have a low affinity for their substrates. 

Ergosterol, the predominant sterol in yeast cells, plays an important role in membrane fluidity, permeability and the activity of many membrane-bound enzymes. In terpene-treated cells, ergosterol synthesis was strongly inhibited, and a global upregulation of genes associated with the ergosterol biosynthesis pathway was described in response to terpene toxicity [80, 121]. 

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