Relationship between Cell Morphology and Intracellular Potassium Concentration in Candida albicans

Abstract

Previously we reported that valinomycin inhibited hyphal growth and induced growth as a chain of yeast cells under hyphal growth induction conditions in Candida albicans. To elucidate the hyphal growth inhibition by valinomycin, we examined the effect of various chemicals on the morphology and found that miconazole inhibited hyphal growth as well as valinomycin: both compounds promoted the leakage of potassium from cells. Analysis of intracellular potassium suggested that hyphal cells contain potassium at high concentrations in comparison with yeast cells. Hyphal growth inhibition by valinomycin was obstructed by the addition of serum. Potassium measurement showed that the addition of serum causes an increase in intracellular potassium, suggesting that the obstruction by serum might be due to an increase in intracellular potassium. The above-mentioned results strongly suggest that the addition of valinomycin and miconazole decreased interacellular potassium and this decrease inhibited hyphal transition.

Plasma-membrane Cnh1 Na+/H+ antiporter regulates potassium homeostasis in Candida albicans

“…To our knowledge this is the first work characterizing the potassium efflux activity of an active transport system directly in C. albicans cells. In C. albicans, changes in intracellular potassium concentration are supposed to influence the development of cell morphology and virulence (Biswas et al, 2000;Watanabe et al, 2006). Our finding that CaCnh1 alkali metal cation/ H + antiporter is, in C. albicans cells, important for the potassium and rubidium tolerance and plays a role in the regulation of intracellular potassium concentration will certainly contribute to elucidating the nature not only of C. albicans high salt tolerance, but also its pathogenicity.…”

“…The morphological switch of C. albicans cells from yeasts to hyphae is associated with a rise in internal pH (Stewart et al, 1988), and the intracellular concentration of K + is higher in cells growing in hyphal form in the presence of serum than in cells growing as yeasts (Watanabe et al, 2006). Although our results showed that deletion of both CNH1 alleles had no significant influence on K + content under conditions of exponential growth of yeast cells in minimal YNB medium, the effect of the absence of CaCnh1p on intracellular potassium concentration in hyphal cells has not yet been estimated.…”

“…The induction of germ-tube formation is associated with a steep rise in internal pH (Stewart et al, 1988), probably due to an increased activity of plasma-membrane H + -extruding ATPase (Kaur & Mishra, 1991;Monk et al, 1993). Previous studies of the effect of alkali metal cations on C. albicans cells revealed that (1) high external concentrations of alkali metal cations (Na + , Li + , K + ) decrease the growth capacity of C. albicans cells (Hermann et al, 2003), (2) an increased extracellular sodium concentration inhibits germ-tube formation (Biswas et al, 2000;Northrop et al, 1997), (3) preincubation with alkali metal cations negatively influences certain C. albicans virulence traits, such as adhesion, cell-surface hydrophobicity and germinating ability (Hermann et al, 2003), and (4) hyphal cells contain a higher concentration of K + than yeast cells (Watanabe et al, 2006). Thus, it is obvious that transport systems mediating fluxes of protons and alkali metal cations across the plasma membrane might play an important role in controlling C. albicans morphology and virulence.…”

Phenyl aldehyde and propanoids exert multiple sites of action towards cell membrane and cell wall targeting ergosterol in Candida albicans

“…The cell envelope of Candida is appeared to be damaged by the compounds as evident by shrinkage of cell surfaces, presence of non-polar bud scars, and receding of cytoplasm leading to lysis of cells. Increase in buds and bud scars implies that compound affect normal division process of yeasts resulting in a single cell with multiple attempt to divide but not resulting in increase in viable number of cells (Watanabe et al 2006). The deposition of vesicles on to the cell surface is an indicative of broken cells releasing cytoplasmic materials upon damage of cell wall and therefore, suggests fungicidal nature of compounds towards yeast cells.…”

“…Estimation of extracellular K + leakage from the fungal cell was performed using the method of (Watanabe et al 2006) with little modifications. Briefly, Candida cells were grown in 100 mL SDB at 30°C, 120 rpm for 24 h. Cell pellets were harvested at 5000 rpm for 5 min and washed three times with sterile PB and suspended in 10 mL of PB.…”