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''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 Hansen's disease (''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.〔James H. Kerr and Terry L. Barrett, "Atypical Mycobacterial Diseases", ''Military Dermatology Textbook'', p. 401.〕 ==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. Many ''Mycobacterium'' species adapt readily to growth on very simple substrates, using ammonia or amino acids as nitrogen sources and glycerol as a carbon source in the presence of mineral salts. Optimum growth temperatures vary widely according to the species and range from 25 °C to over 50 °C. Some species can be very difficult to culture (i.e. they are fastidious), sometimes taking over two years to develop in culture. Further, some species also have extremely long reproductive cycles — ''M. leprae'', may take more than 20 days to proceed through one division cycle (for comparison, some ''E. coli'' strains take only 20 minutes), making laboratory culture a slow process.〔 In addition, the availability of genetic manipulation techniques still lags far behind that of other bacterial species. A natural division occurs between slowly– and rapidly–growing species. Mycobacteria that form colonies clearly visible to the naked eye within seven days on subculture are termed rapid growers, while those requiring longer periods are termed slow growers. Mycobacteria cells are straight or slightly curved rods between 0.2 and 0.6 µm wide by 1.0 and 10 µm long. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mycobacterium」の詳細全文を読む スポンサード リンク
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