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English definition of “bacterium”

bacterium

noun [C usually plural] uk   /bækˈtɪə.ri.əm/ us    /-ˈtɪr.i-/ (plural bacteria)
C1 a type of very small organism that lives in air, earth, water, plants, and animals, often one that causes disease: an illness caused by bacteria in drinking water The bacterium Streptococcus pneumoniae causes about a third of some 3,000 annual meningitis cases.Bacteria, moulds, germs and viruses
(Definition of bacterium from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
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