Influence of surrounding media on preservation of cell wall ultrastructure of Candida albicans revealed by low temperature scanning electron microscopy.

Influence of surrounding media on the surface structures of the cell wall of Candida albicans was discussed with respect to the preservation of ultrastructure during the specimen preparation for scanning electron microscopy. The fibrillar structure of the cell surface was distinctly identified by the rapid-freezing technique. It was difficult, however, to observe this structure by the conventional specimen preparation technique. The reason for the difference between these two preparation techniques was studied using a low temperature SEM. Through investigating the influence of each step of the conventional technique on the fibrillar structure, it was found that the fibrils were drastically deformed and disappeared during the dehydration step in ethanol above 80% in concentration. In order to study which physicochemical properties participated in this disappearance phenomenon, yeast cells were treated with various media: solutions in different pH ranges and at different salt concentrations, ionic solutions, surfactants, formamide, dimethyl sulfoxide, acetone and Fehling's solution. As a result, the fibrillar structure was found well preserved when the medium had an affinity for the constituent molecules of the fibrils. When without affinity, the fibrils suffered a remarkable deformation. The mechanism of this deformation is discussed in terms of molecular interaction of solute and solvent.