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n. pl. ac·tin·o·bac·ter·i·a (-tîr′ē-ə)
Any of various gram-positive bacteria of the phylum Actinobacteria, which includes bacteria that live in the soil and in the digestive tract, as well as pathogens such as those that cause tuberculosis and leprosy. Some actinobacteria are used to produce antibiotics and certain dairy products.
[From New Latin Actīnobactēria, phylum name : Actīnomykēs, type genus of the phylum; see actinomyces + bacterium.]