Analysis of the Capsule of Mycobacterium tuberculosis

Mycobacterium tuberculosis and the other pathogenic mycobacteria examined so far by electron microscopy are seen to be surrounded within host cells by an electron-transparent zone (ETZ). For Mycobacterium lepraemurium, this space between the phagosomal membrane of the infected cellthe wall of the enclosed bacteria was called a "capsular space" (1). Using light microscopic techniques (2-4), Hanks demonstrated the presence of an unstainable "halo" around some pathogenic mycobacteria and pointed out (5) that what appeared to be a capsule could be seen in several published images of pathogenic mycobacteria.