The permeability of mycobacteria to substances in their environment is controlled by the properties of their envelopes.
More lipophilic molecules can diffuse through the lipid layer.
Mycobacteria secrete proteins into their environment, which are likely to be important in the pathogenesis of mycobacterial diseases. Knowledge of how these proteins, and the polysaccharides of the capsule, cross the outer lipid barrier is minimal at present. It is likely that proper knowledge of mycobacterial permeability will enable new approaches to treatment of mycobacterial disease.