Expansion of the Candida albicans cell envelope in different morphological forms of the fungus.

Modes of cell envelope expansion were monitored in developing cells of Candida albicans 73/055 to which polystyrene beads were attached. Eight different conditions of culture medium, pH and temperature were used to promote growth in a variety of morphological forms. The cells were observed microscopically during growth in Sykes-Moore perfusion chambers, and sequential measurements of distances between the bead and the parent cell, and the bead and the apical tip were used to distinguish apical envelope expansion from general envelope expansion. Morphology index (Mi) was determined at each time point as an estimate of each cell's morphology. Calculations based on the measurements showed that general envelope expansion was inversely proportional to Mi, but that general expansion greater than 20% occurred only in cells with a final Mi less than 2.0, indicating that regulation of apical and general envelope expansion alone may be insufficient to determine the different morphologies seen in cells with higher Mi. The rate of expansion of the perimeter of cells was linearly proportional to the final Mi. This observation suggests that commitment to morphological development in C. albicans may in part involve commitment to a rate of envelope expansion, which itself helps determine the final morphology of a cell.