bacteriumbacterium /bækˈtɪriəm/ ●○○ noun (plural bacteria /-riə/) [countable] 
science, biology a tiny organism with a single cell. Some bacteria cause disease, but others are very important in natural processes such as fermentation.—bacterial adjective: a bacterial infection
science, biology a tiny organism with a single cell. Some bacteria cause disease, but others are very important in natural processes such as fermentation.—bacterial adjective: a bacterial infection