It is also used in the brewing process for beers, wines, and alcoholic beverages. Well it is a fungus. Yeast are microscopic, one celled organisms. These wonderful organisms range in size from 1-30 microns in diameter. Many different kinds of yeast have been identified.
Wild yeast is everywhere.
This may cause a real problem for brewers, the article says. Wild yeast cells are carried from place to place by air and dust. Yes if the conditions are right they will grow and divide. They grow very fast. Yeast reproduce by the process budding.