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 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 cultures. (Mycobacteria are not, however, fungi, which are eukaryotes, while all bacteria are prokaryotes.)

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 fast. Mycobacteria have an outer membrane. They do not have 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, which is 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.