<Tr> <Td_colspan="2"> <P> See below . </P> </Td> </Tr> <P> See below . </P> <P> Mycobacterium is a genus of Actinobacteria, given its own family, the Mycobacteriaceae . Over 190 species are recognized in this genus . This genus includes pathogens known to cause serious diseases in mammals, including tuberculosis (Mycobacterium tuberculosis) and leprosy (Mycobacterium leprae) in humans . 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 cultures . It has a positive gram stain and a spirochete spine . </P> <P> 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 fast . Mycobacteria have an outer membrane . They possess capsules, and most do not form endospores . Mycobacterium marinum and perhaps M. bovis have been shown to sporulate; however, this has been contested by further research . The distinguishing characteristic of all Mycobacterium species is that the cell wall is thicker than in many other bacteria, being hydrophobic, waxy, and rich in mycolic acids / mycolates . The cell wall consists of the hydrophobic mycolate layer and a peptidoglycan layer held together by a polysaccharide, arabinogalactan . The cell wall makes a substantial contribution to the hardiness of this genus . The biosynthetic pathways of cell wall components are potential targets for new drugs for tuberculosis . </P>

Tuberculosis is caused by an organism of the genus