actinomycete

—actinomycetous, adj.

/ak tin'oh muy"seet, -muy seet", ak'teuh noh-/, n. Bacteriol.

any of several rod-shaped or filamentous, aerobic or anaerobic bacteria of the phylum Chlamydobacteriae, or in some classification schemes, the order Actinomycetales, certain species of which are pathogenic for humans and animals.

[1915-20; prob. through construal of NL Actinomycetes (pl. of ACTINOMYCES) as an E pl. n.; see -MYCETE]

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Any of a group of generally low-oxygen–utilizing bacteria identified by a branching growth pattern that results in large threadlike structures.

The filaments may break apart to form rods or spheroidal shapes. Some actinomycetes can form spores. Many species occur in soil and are harmless to animals and higher plants; others are important disease-causing agents. For diagnostic purposes in human infections, the presence of sulfur granules is used.

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▪ bacteria

 any member of a heterogeneous group of gram-positive, generally anaerobic bacteria noted for a filamentous and branching growth pattern that results, in most forms, in an extensive colony, or mycelium. The mycelium in some species may break apart to form rod- or coccoid-shaped forms. Many genera also form spores; the sporangia, or spore cases, may be found on aerial hyphae, on the colony surface, or free within the environment. Motility, when present, is conferred by flagella. Many species of actinomycetes occur in soil and are harmless to animals and higher plants, while some are important pathogens, and many others are beneficial sources of antibiotics.

      Many authorities recognize eight different groups of actinomycetes, though these groups are themselves heterogeneous and will require further study to classify fully. Of the specific types of actinomycetes, Nocardia asteroides causes tissue infections in humans, and Dermatophilus congolensis causes dermatophilosis, a severe dermatitis of cattle, sheep, horses, and occasionally humans. Several species of Streptomyces cause the disease actinomycosis in humans and cattle. Many of the actinomycetes are sources of antibiotics (antibiotic) such as streptomycin.

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