Saccharomyces
Saccharomyces is a genus of fungi that includes many species of yeasts. Saccharomyces is from Greek σάκχαρ (sugar) and μύκης (mushroom) and means sugar fungus. Many members of this genus are considered very important in food production. It is known as the brewer's yeast or baker's yeast. They are unicellular and saprophytic fungi. One example is Saccharomyces cerevisiae, which is used in making wine, bread, and beer. Other members of this genus include the wild yeast Saccharomyces paradoxus that is the closest relative to S. cerevisiae, Saccharomyces bayanus, used in making wine, and Saccharomyces boulardii, used in medicine.
Colonies of Saccharomyces grow rapidly and mature in three days. They are flat, smooth, moist, glistening or dull, and cream in color. The inability to use nitrate and ability to ferment various carbohydrates are typical characteristics of Saccharomyces.
Generally, they have a diameter of 2-8μm and length of 3-25μm. Blastoconidia (cell buds) are observed. They are unicellular, globose, and ellipsoid to elongate in shape. Multilateral (multipolar) budding is typical. Pseudohyphae, if present, are rudimentary. Hyphae are absent.
Saccharomyces produces ascospores, especially when grown on V-8 medium, acetate ascospor agar, or Gorodkowa medium. These ascospores are globose and located in asci. Each ascus contains 1-4 ascospores. Asci do not rupture at maturity. Ascospores are stained with Kinyoun stain and ascospore stain. When stained with Gram stain, ascospores appear Gram-negative, while vegetative cells appear Gram-positive.
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