An aerobic gram-positive organism that develops aerial and vegetative branched filaments. The colonies are small, leathery and have a granular, powdery or velvety appearance due to the aerial mycelium present. Colonies may be cream to dark brown or black and produce an earthy odor. It has been isolated from soil, plants, dust, water, compost, and manure. It causes human infections following inhalation of these bacteria or by contamination of an area of trauma.