Bacteria

A large class of microscopic unicellular organisms occurring in three main forms: spiral (spirilla), spherical (coccus), and rod-shaped (bacillus). Bacteria are found in soil, water, and organic matter as well as in living plants and animals. Bacterial growth causes a chemical effect that is significant in food production in ways that are both beneficial and harmful. As they reproduce, bacteria cause fermentation, which is necessary and desirable in yeast development and in the transformation of milk into yogurt, for example, but bacteria are also responsible for food spoilage and food-borne illness.