Yeast, a microscopic, one-celled organism belonging to the group of
organisms called fungi. There are many kinds of yeasts, some of them of
great importance to humans. Yeast is necessary to make leavened bread,
beer, cheese, wine, and whiskey. It is rich in B vitamins; a form of
yeast called brewer’s yeast is used as a diet supplement. Yeast is also
used in genetic engineering to produce large quantities of certain
hormones and enzymes, which are used for such medical purposes as
healing wounds and reducing inflammation. Some types of yeast, however,
cause disease; candidiasis, a skin infection, is an example.
