ABSTRACT
Actinomycetes are groups of heterogeneous gram-positive anaerobic bacteria-except for Frankia, a gram-negative actinomycete-which are characterized by their filamentous growth pattern that results in an extensive colony or mycelium formation. The mycelium in some species may break apart to form rods or cocci. Many genera also form spores; the sporangia, or spore case may be formed 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 the soil and are harmless to animals and higher plants, while some are important pathogens, and still others are beneficial sources of antibiotics.
