Mycobacterium

Mycobacterium is a genus of Actinobacteria, given its own family, the Mycobacteriaceae. The genus includes pathogens known to cause serious diseases in mammals, including tuberculosis (Mycobacterium tuberculosis) and the classic Hansen's strain of leprosy (Mycobacterium leprae). The Greek prefix myco- means "fungus," alluding to the way mycobacteria have been observed to grow in a mold-like fashion on the surface of liquids when cultured.
Microbiologic characteristics
Mycobacteria are aerobic and nonmotile bacteria (except for the species Mycobacterium marinum, which has been shown to be motile within macrophages) that are characteristically acid-alcohol-fast. Mycobacteria do not contain endospores or capsules and are usually considered Gram-positive. While mycobacteria do not seem to fit the Gram-positive category from an empirical standpoint (i.e., in general, they do not retain the crystal violet stain well), they are classified...