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The related yeasts Saccharyomyces cervisiae and Candida albicans can grow by producing a bud which is identical to the mother cell. What other forms of growth and development do these species undergo? Is there a connection between different growth forms and infection of humans by Candida?

C. albicans and S. cervisiae are both able to grow as pseudohyphae and yeast. In C. albicans there is a third growth form, the hyphal growth form.

In the presence of varying concentrations of nutrients, S. Cervisiae cells may adopt a number of different fates. In the presence of favourable environmental conditions, i.e. abundant nitrogen supply and abundant fermentable carbon source, S. Cervisiae will adopt the yeast form, characterized by asymmetric budding, and proliferate. If nutrients are limited but not exhausted, e.g. a limiting nitrogen source and an abundant fermentable carbon source, S. Cervisiae will switch from the yeast form to a filamentous form. This is known as pseudohyphal differentiation, and growth in this form produces pseudohyphae. When nutrients are exhausted, i.e. limiting nitrogen source, limiting fermentable carbon source, S. Cervisiae will undergo sporulation producing spores. (1, lecture notes).

C. albicans cells assume different growth forms and morhologies depending on environmental conditions. In cultures grown at low temperature and/or pH, e.g below 30 C or pH 4.0 the yeast form is prevalent. Hyphae develop from yeast cells in a response to a number of growth conditions including; temperatures above 34 C in the presence of Serum, in Lees medium at 37 C, in cultures at 37 C and neutral pH, and in the presence of N-acetylglucosamine. Given any of these environmental conditions the majority of growth is hyphal. Cultures grown in intermediate temperatures and pH are seen to contain pseudohyphae. Pseudohyphae can be reliably induced in cultures at pH 6.0 and 35 C, in Nitrogen limited growth on a solid medium...