Yeasts

Yeasts comprise an unrelated grouping of fungi whose primary growth form is not filamentous but rather unicellular. There are approximately 80 genera of fungi that grow as yeasts, representing about 600 species (7). Yeasts are well known as common commensals of animal mucosa (e.g. Candida, Geotrichum), where they are occasionally associated with disease mostly where immunological predisposition occurs [12]). A number of yeasts and yeast-like fungi occur in environmental settings where water films exist (13,14). Due to the paucity of structure demonstrated by most yeasts, their identification usually involves a battery of physiological and nutritional tests, similar to bacterial identification (13). The study of yeasts (Zymology) long remained independent of the rest of mycology despite that the organisms themselves are true fungi. Yeast identification remains beyond the scope of general mycology.