GENERAL MICROBIOLOGY - T.P. Pirog - 2004

9. YEASTS

Nowadays, Yeasts are regarded as a group of higher Fungi that predominantly vegetate in a unicellular form and reproduce by budding or fission. Yeasts are classified as fungi based on A number of characteristic features: the presence of a Nucleus, the absence of Photosynthetic Pigments and motility, and the presence of Glycogen as a reserve substance. In most yeasts, the Cells are colorless, while some species synthesize red, orange, or yellow pigments.

Yeasts vary in the shape of their vegetative cells, sexual spores, and cultural characteristics. As a rule, they grow within a Temperature range from 0 to 37º C, can develop under aerobic and anaerobic conditions at a pH of 3 to 8, and the lower limit of Water activity is 0.90-0.60.

Like all fungi, yeasts are characterized by an adsorptive type of Nutrition. Most of them are Saprophytes, occurring in the phyllosphere and rhizosphere of plants, soil, marine and fresh water, and other natural substrates. Yeasts also develop in the gastrointestinal tract and on the Skin surface of animals. Some of them are able to exist in A wide variety of ecological niches, while others are restricted to specific, sharply limited conditions. Over 500 Yeast species belonging to more than 60 genera have been described.



Last update: 13/08/2026

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