Analysis of the Lipids of Mycobacterium tuberculosis

Mycobacterial cell wall ultrastructure has been studied through the use of negative staining, electron microscopy (1 ,2 ), freeze fracture (3 ), X-ray diffraction (4 ), differential scanning calorimetry (5 ,6 ), and electron spin resonance spectroscopy. Through the use of these techniques, the cellular envelope has been shown to be highly ordered and organized in a tripartite structure (2 ,3 ,7 ,8 ). Classical freeze-fracture and freeze-etch electron microscopy studies have established that fragmentation takes place along extended lipid-rich nonaqueous domains. Applied to mycobacteria, these techniques have revealed two fracture sites, an inner cleavage plane within the plasmalamellar membrane and an outer cleavage plane between the mycolic acids and the tenuous outer leaflet (1 ). These two cleavage sites represent the two domains containing the majority of the lipid material of the bacillus.