Trk1-mediated potassium uptake contributes to cell-surface properties and virulence of Candida glabrata

The absence of high-affinity potassium uptake in Candida glabrata, the consequence of the deletion of the TRK1 gene encoding the sole potassium-specific transporter, has a pleiotropic effect. Here, we show that in addition to changes in basic physiological parameters (e.g., membrane potential and intracellular pH) and decreased tolerance to various cell stresses, the loss of high affinity potassium uptake also alters cell-surface properties, such as an increased hydrophobicity and adherence capacity. The loss of an efficient potassium uptake system results in diminished virulence as assessed by two insect host models, Drosophila melanogaster and Galleria mellonella, and experiments with macrophages. Macrophages kill trk1Δ cells more effectively than wild type cells. Consistently, macrophages accrue less damage when co-cultured with trk1Δ mutant cells compared to wild-type cells. We further show that low levels of potassium in the environment increase the adherence of C. glabrata cells to polystyrene and the propensity of C. glabrata cells to form biofilms

Vliv stárnutí populace na spotřebu a životní úroveň

Sychrová, H. The impact of people ageing on consumption and living standards. Diploma thesis. Brno: Mendel University, 2018. The diploma thesis deals with ageing of population and its impact on consumption and living standard in the Czech republic. The thesis explores the selected indicators of living standard and compares development of incomes and spending of individual generations. In the thesis, there are used techniques of marketing research, specifically questionnaire and in-depth interviews. The output of the thesis is to evaluate living standard of seniors and expectation of young generations

Metals and their fate in the environment

Tato bakalářská práce pojednává o výskytu kovů ve složkách životního prostředí. Práce dále obsahuje charakteristiku vybraných kovů, popis mechanismů přeměn jejich forem a vlivy pH, oxidačně-redukčního potenciálu, kyslíku a dalších faktorů na tyto mechanismy. Práce popisuje mobilitu kovů, její význam pro rostliny a dekontaminační technologie. V závěru jsou uvedeny příklady chování kovů ve složkách životního prostředí.This bachelor thesis is about the occurrence of metals in the environment. The work also includes the characteristics of selected metals and the description of mechanisms of transformation of their forms. The influence of pH, the oxidation-reduction potential, the presence of oxygen etc. on these mechanisms is explained. This work describes the mobility of metals, its importance for plants and decontamination technologies. In the end, there are examples of behavior of metals in the environment.Ústav environmentálního a chemického inženýrstvíPosluchačka seznámila komisi s obsahem své bakalářské práce a následně zodpověděla dotazy komise. Citace literatury. Jednotka hustoty kovů. Ukládání kovů v organismech, otrava arzenem - analýza vlasů. Dekontaminační technologie - odčerpávání půdního vzduchu. Kovy v ovzduší. Nebezpečnost dimethylrtuti

Yeast Trk1 Potassium Transporter Gradually Changes Its Affinity in Response to Both External and Internal Signals

Yeasts need a high intracellular concentration of potassium to grow. The main K+ uptake system in Saccharomyces cerevisiae is the Trk1 transporter, a complex protein with four MPM helical membrane motifs. Trk1 has been shown to exist in low- or high-affinity modes, which reflect the availability of potassium in the environment. However, when and how the affinity changes, and whether the potassium availability is the only signal for the affinity switch, remains unknown. Here, we characterize the Trk1 kinetic parameters under various conditions and find that Trk1’s KT and Vmax change gradually. This gliding adjustment is rapid and precisely reflects the changes in the intracellular potassium content and membrane potential. A detailed characterization of the specific mutations in the P-helices of the MPM segments reveals that the presence of proline in the P-helix of the second and third MPM domain (F820P and L949P) does not affect the function of Trk1 in general, but rather specifically prevents the transporter’s transition to a high-affinity state. The analogous mutations in the two remaining MPM domains (L81P and L1115P) result in a mislocalized and inactive protein, highlighting the importance of the first and fourth P-helices in proper Trk1 folding and activity at the plasma membrane

Changes in the Sterol Composition of the Plasma Membrane Affect Membrane Potential, Salt Tolerance and the Activity of Multidrug Resistance Pumps in Saccharomyces cerevisiae.

We investigated the impact of the deletions of genes from the final steps in the biosynthesis of ergosterol (ERG6, ERG2, ERG3, ERG5, ERG4) on the physiological function of the Saccharomyces cerevisiae plasma membrane by a combination of biological tests and the diS-C3(3) fluorescence assay. Most of the erg mutants were more sensitive than the wild type to salt stress or cationic drugs, their susceptibilities were proportional to the hyperpolarization of their plasma membranes. The different sterol composition of the plasma membrane played an important role in the short-term and long-term processes that accompanied the exposure of erg strains to a hyperosmotic stress (effect on cell size, pH homeostasis and survival of yeasts), as well as in the resistance of cells to antifungal drugs. The pleiotropic drug-sensitive phenotypes of erg strains were, to a large extent, a result of the reduced efficiency of the Pdr5 efflux pump, which was shown to be more sensitive to the sterol content of the plasma membrane than Snq2p. In summary, the erg4Δ and erg6Δ mutants exhibited the most compromised phenotypes. As Erg6p is not involved in the cholesterol biosynthetic pathway, it may become a target for a new generation of antifungal drugs

The Candida albicans Na+/H+ antiporter exports potassium and rubidium

AbstractThe Candida albicans Cnh1p belongs to the family of Na+/H+ antiporters (TC 2.A.36) but it transports besides toxic sodium and lithium also rubidium and potassium. Upon heterologous expression in a Saccharomyces cerevisiae salt-sensitive strain, the Cnh1p is targeted to the plasma membrane and its transport activity results in increased tolerance of cells to external alkali metal cations. The cation efflux activity of Cnh1p in S. cerevisiae depends on the gradient of protons across the plasma membrane, and a Cnh1p-mediated K+ efflux is involved in a cell response to sudden rise of cytoplasmic pH

Strains with hyperpolarized membranes are less tolerant to LiCl and cationic drugs.

<p>(A) Relative membrane potential of BY4741 (black circles), <i>erg2Δ</i> (red squares), <i>erg3Δ</i> (green triangles), <i>erg4Δ</i> (yellow triangles), <i>erg5Δ</i> (blue diamonds) and <i>erg6Δ</i> (cyan hexagons) cells estimated with diS-C₃(3) fluorescence probe. (B) Relative growth in liquid YPD medium supplemented with 100 mM LiCl (growth in YPD medium without LiCl = 100%). The <i>P</i> values (*<i>P</i> < 0.05, **<i>P</i> < 0.001) denote statistically significant differences from the wild-type strain. (C) Growth on solid YPD media supplemented with LiCl, hygromycin B and tetramethylammonium (TMA) after 1 day of incubation.</p

Activity of Pdr5 and Snq2 pumps.

<p>Changes in diS-C₃(3) staining of (A) wild-type BY4741 (black circles), <i>erg5</i>Δ (blue diamonds), <i>pdr5</i>Δ (pink squares), <i>snq2</i>Δ (violet hexagons) and (B) <i>erg2</i>Δ (red squares), <i>erg3</i>Δ (green triangles), <i>erg4</i>Δ (yellow triangles) and <i>erg6</i>Δ (cyan hexagons) cells after addition of 10 μM CCCP (full symbols); control (empty symbols). (C) Changes in diS-C₃(3) staining of wild-type cells (grey and black symbols) after addition of CCCP or FK506: 5 μM CCCP (diamonds), 10 μM CCCP (squares), 20 μM CCCP (inverted triangles), 10 μM FK506 (hexagons), 100 μM FK506 (triangles), control (circles) in comparison with staining of <i>pdr5</i>Δ (pink symbols) and <i>snq2</i>Δ cells (violet symbols): 10 μM CCCP (squares), 10 μM FK506 (hexagons), control (circles). (D) Changes in diS-C₃(3) staining of wild-type (black circles), <i>erg2</i>Δ (red squares), <i>erg3</i>Δ (green triangles), <i>erg4</i>Δ (yellow triangles), <i>erg5</i>Δ (blue diamonds), <i>erg6</i>Δ (cyan hexagons), <i>pdr5</i>Δ (pink squares) and <i>snq2</i>Δ (violet hexagons) cells after addition of 100 μM FK506 (full symbols); control (empty symbols). Arrows with dotted lines indicate addition of compounds. (E) Growth inhibition zones of cells exposed to 30 mM FK506, 6.5 mM fluconazole, 5 mM NQO and their combinations.</p

Growth inhibition zones of cells exposed to antifungal drugs.

<p>Red frames indicate strains less tolerant to drugs than the wild type, green frames indicate more tolerant strains than the wild type. Diameter of paper discs was 6 mm. The <i>P</i> values (*<i>P</i> < 0.05, **<i>P</i> < 0.01, ***<i>P</i> < 0.001) denote statistically significant differences from the wild-type strain.</p