Characterization of cell wall proteins of yeast and hydrophobic mycelial cells of Candida albicans

Abstract

Cell surface hydrophobicity (CSH) of blastoconidia and blastoconidia bearing germ tubes of Candida albicans ATCC 26555 was monitored by assessing attachment of polystyrene microspheres to the cell surface, and we found that mature hyphae were significantly hydrophobic. Treatment of intact cells with low concentrations of beta-glucanase (Zymolyase 20T) or proteases abolished or significantly reduced attachment of latex beads to hyphae. This effect paralleled an obvious reduction in CSH of the entire cell population, as measured by an aqueous-hydrocarbon biphasic partitioning assay. Analysis of the cell wall material released by Zymolyase and adsorbed on polystyrene microspheres indicated that germ tube-specific cell wall proteins and mannoproteins with apparent molecular masses of 20 to 67 kDa may be responsible for the hydrophobicity of hyphae. Zymolyase released from blastoconidia cell walls a different set of proteins and mannoproteins that were able to adsorb to polystyrene microbeads. Such molecular species might in turn be responsible for the CSH exhibited by blastoconidium populations as determined by the biphasic partitioning assay, although these probably hydrophobic components can be masked on the surface of blastoconidia, as the latter had no or very few latex microspheres attached to their surfaces. Treatment of cells of both C. albicans morphologies with 2-mercaptoethanol released qualitatively distinct species of polystyrene-adsorbed proteins and mannoproteins from yeast and mycelial cells. These observations suggested that hydrophobic proteins and mannoproteins that could be associated with CSH are bound to the cell wall structure through diverse types of linkages.