Molecular biology of chitin synthesis in Candida albicans
The genus Candida contains about 200 species, most of which cannot be differentiated on morphology alone, but they can be identified using physiological characteristics such as assimilation of different nitrogen sources, fermentation of sugars and inhibition of growth. The genus Candida is composed of an extremely heterogeneous group of organisms that grow as yeast forms (blastoconidia), and most members of the genus also produce filamentous growth forms (pseudohyphae, pseudomycelium or/and true hyphae). In addition, C. albicans and C. dubliniensis also have the ability to form true hyphae and chlamydospores. Thus, C. albicans is pleiomorphic and undergoes reversible morphogenetic transitions between budding, pseudohyphal and hyphal forms (Odds, 1988; Kerridge, 1993). Pseudohyphae range from relatively short to extended cells and unlike hyphae they have constrictions at their septa (Merson-Davies and Odds, 1989; Sudbery, 2001). C. albicans can also form chlamydospores, asexual spores that are formed by rounding off of a cell or cells from a suspensor cell. These generally appear under unfavourable conditions and in media of high carbon/nitrogen ratio (Kurtz et al., 1990). Candidiasis is an endogenous disease, but it can be transmitted laterally for example from health care workers to patients or between sexual partners, and vertically, as from mother to the neonate (Calderone, 2002b). In its commensal phase, C. albicans usually grows in the form of yeast cells (Poulain et al., 1985), whereas yeast cells, hyphae and pseudohyphae are all observed in infected tissue. C. albicans is found in the normal gastrointestinal flora of most healthy humans. Its normal habitat is the digestive tract of warm-blooded animals from which the fungal species is most frequently isolated. It has been found that 2 to 70% of individuals carry C. albicans in the oral cavity (Odds, 1988).