title: Effect of pH, carbon source and K+ on the Na+-inhibited germ tube formation of Candida albicans.
abstract: The effect of pH, carbon source and K+ on the Na+ -inhibited germ tube formation of the pathogenic fungus Candida albicans was examined in the arginine-phosphate modified (APM) medium. All C. albicans cells formed germ tubes in APM medium at pH 5.0-9.0. Na+ inhibited germ tube formation in a concentration dependent manner ranging from 0.2 to 1.0 M, and was further influenced by the pH of the medium. The inhibitory effect of Na+ was lowest at pH 8.0, and germ tube formation ceased at 1.0 M Na+ for any pH (4.0-9.0). At pH > or = 6.0, non-germ tube-forming cells did not show yeast growth; whereas at pH < or = 5.0, Na+ inhibited only germ tube formation but did not inhibit yeast growth. The inhibitory effect of Na+ was stronger in glucose medium than in galactose medium as carbon source. K+, at 0-0.8 M, had almost no effect on germ tube formation. However, in the presence of Na+, a very low concentration of K+ (0.5 mM) was able to release the cells from Na+ arrest and produced an increase in the rate as well as the percentage of germ tube formation. Intracellular Na+/K+ ratios increased with the increase in extracellular Na+ concentration, whereas the ratios decreased and remained within nontoxic levels when the extracellular K+ concentration was increased.
authors.affiliation: Research Center for Pathogenic Fungi and Microbial Toxicoses, Chiba University, Inohana, Japan.
authors.forename: S K
authors.initials: SK
authors.lastname: Biswas
authors.forename: K
authors.initials: K
authors.lastname: Yokoyama
authors.forename: K
authors.initials: K
authors.lastname: Nishimura
authors.forename: M
authors.initials: M
authors.lastname: Miyaji
mesh_terms: D002176:Candida albicans / Q000254:growth & development*; D002244:Carbon / Q000378:metabolism; D003470:Culture Media; D006863:Hydrogen-Ion Concentration; D009024:Morphogenesis; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology
chemical_list: D003470:Culture Media; D002244:Carbon; D012964:Sodium; D011188:Potassium