Morphological Change in Candida albicans

Abstract

Candida albicans not only forms yeasts, pseudohyphae and true hyphae, but those hyphae also posses properties of thigmatropism (responding to surface contact) and electrotropism (responding to electric fields). The pleomorphic character of C. albicans can now be objectively measured for individual cells and for growing populations by means of a “morphology index” (Mi) that has shown general envelope expansion to be a property only of yeast cells with Mi<2 and surface expression of “hypha-specific” antigenic epitopes to be a property of hyphal cells with Mi>3. By contrast, cellular chitin content and rate of cell envelope expansion are parameters that increase in proportion with Mi. Cell shape is thus a consequence of the interplay of separately regulated processes, some of which are expressed exclusively in the development of particular morphologies while others are expressed continuously but vary quantitatively with morphology. The discovery of morphology-specific genes that are expressed only in hyphal forms, and of pH-specific genes, one of which is critical for hyphal development, offers the possibility of future insights into the molecular regulation of morphogenesis in C. albicans.