Surface-active properties of Candida albicans

Cell surface hydrophobicity may be an important factor contributing to the virulence of Candida yeast cells. Surface hydrophobic and surface polar groups would be required for a yeast cell to act as a surface-active agent. In this report, the surface activities of whole yeast cells were measured. Yeast cells added at 10⁸/ml reduced the surface tension (γ(s)) of saline by 20% as determined by the du Nouy method. A 1% suspension of yeast cell wall fragments reduced γ(s) of saline by 36%. Whole yeast cells caused a reduction in interfacial tension (γ(I)) between hexadecane and saline. The reduction of γ(I) was proportional to the surface hydrophobicity of the yeasts. Yeast cells grown in glucose as the sole carbon source (thus possessing a relatively more hydrophilic cell surface) reduced γ(I) by 30%, whereas yeast cells grown in hexadecane (thus possessing a more hydrophobic cell surface) reduced γ(I) by 41%. The reduction of γ(I) was reversed upon the addition of a strong surfactant. It was also demonstrated that yeast cells blended with nonionic surfactants during growth in a glucose broth in order to change their cell surface hydrophobicity adhered to solid surfaces in direct proportion to their cell surface hydrophobicity. Thus, the surface-active properties of Candida yeast cells may significantly contribute to the accumulation of yeast cells at various biological interfaces such as liquid-solid, liquid-liquid, and liquid-air leading to their eventual adhesion to solid or tissue surfaces.