Physical organization of lipids in the cell wall of Mycobacterium chelonae.

Mycobacterial cell wall functions as an effective permeability barrier, making these bacteria resistant to most antibacterial agents. It has been assumed that this low permeability was due to the presence of a large amount of unusual lipids in the cell wall, but it was not known how these lipids are able to produce such an exceptional barrier. We report here the first experimental evidence on the physical arrangement of these lipids based on X-ray diffraction studies of purified Mycobacterium chelonae cell wall, a result suggesting that the hydrocarbon chains of the cell-wall lipids are arranged predominantly in a direction perpendicular to the cell wall surface, probably producing an asymmetric bilayer structure.