S. cerevisiae is a common environmental fungus and transient component of the normal flora of the gastrointestinal tract and skin, however it is not normally considered to be a pathogen. Most often it is found in areas where fermentation can occur, such as the on the surface of fruit, storage cellars and on the equipment used during the fermentation process. It is believed that it was first discovered on the skins of grapes.
Colonies are white to cream coloured, smooth, glabrous and yeast-like in appearance. Microscopic morphology shows large, globose to ellipsoidal budding yeast-like cells.
S. cerevisiae is famously known for its role in food production. It is the critical component in the fermentation process that converts sugar into alcohol. It is also used in the baking process as a leavening agent; yeast releasing gas into their environment results in the spongy-like texture of breads and cakes.
It is one of the most intensively studied eukaryotic model organisms in molecular and cell biology, much like Escherichia coli as the model bacterium. Its big advantage is that it is both a unicellular and eukaryotic organism. Another advantage is its fast growth grate. On a normal yeast medium, it takes 90 minutes for the yeast population to double and colonies are usually visible 2-3 days after placing them on fresh medium.
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Microbiology Safety Considerations.This guide for Australian schools is made available through the courtesy of the author, S K Hoffmann.
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Bacterial and Fungi Cultures Note(new window, 0.1M, pdf format)