Humans derive substantial benefits from the activities of microorganisms. For example, many microbial species live in and on various parts of the body and prevent pathogenic bacteria from gaining a foothold. These organisms are referred to as normal flora. Microorganisms produce many of the foods we eat, including fermented dairy products (sour cream, yogurt, and buttermilk), as well as fermented foods such as pickles, sauerkraut, breads, and alcoholic beverages. In industrial corporations, microbes are cultivated in huge quantities and used to produce vitamins, enzymes, organic acids, and other essential growth factors.
