Food microbiology is a subdiscipline in the field of microbiology concerned with the study of bacteria, fungi, and viruses that grow in or are transmitted by foods. While bacteria are frequently associated with food spoilage and food poising, some species preserve foods through fermentation or produce food ingredients. Microbiology can be defined as the biology of microscopic organisms, or life too small to be seen with the naked eye. Microbiology covers several disciplines, including virology (study of viruses), bacteriology (study of bacteria), mycology (study of fungi), and parasitology (study of parasites). Each of these disciplines may include but is not limited to studies of infectious disease - causing microorganism.