- plural noun very small organisms, invisible except through a microscope, belonging to a large group, some of which help in the decomposition of organic matter, some of which are permanently in the intestines of animals and can break down food tissue and some of which cause disease
- The plural form of bacterium. Important in the food industries are Salmonella, Bacillus cereus, Campylobacter, Staphylococcus, Listeria, all of which are food poisoning organisms and Lactobacillus spp. and Streptococcus spp., etc. which are used in the production of various foodstuffs. See under each heading.
- microorganisms that help in the decomposition of organic matter but can cause disease and spoil wine. The main bacterium causing problems in winemaking is Acetobacter, which converts alcohol to acetic acid in the presence of oxygen.