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The Acid-Fast Cell Wall

المؤلف:  Stefan Riedel, Jeffery A. Hobden, Steve Miller, Stephen A. Morse, Timothy A. Mietzner, Barbara Detrick, Thomas G. Mitchell, Judy A. Sakanari, Peter Hotez, Rojelio Mejia

المصدر:  Jawetz, Melnick, & Adelberg’s Medical Microbiology

الجزء والصفحة:  28e , p30

2026-03-29

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Some bacteria, notably the tubercle bacillus (M. tuberculosis) and its relatives, have cell walls that contain substantial amounts of waxes, complex branched hydrocarbons (70–90 carbons long) known as mycolic acids. The cell wall is composed of peptidoglycan and an external asymmetric lipid bilayer; the inner leaflet contains mycolic acids linked to an arabinoglycan, and the outer leaflet contains other extract able lipids. This is a highly ordered lipid bilayer in which proteins are embedded, forming water-filled pores through which nutrients and certain drugs can pass slowly. Some compounds can also penetrate the lipid domains of the cell wall albeit slowly. This hydrophobic structure renders these bacteria resistant to many harsh chemicals, including deter gents and strong acids. If a dye is introduced into these cells by brief heating or treatment with detergents, the dye cannot be removed by dilute hydrochloric acid, as in other bacteria. These organisms are therefore called acid fast. The permeability of the cell wall to hydrophilic molecules is 100- to 1000 fold lower than for E. coli and may be responsible for the slow growth rate of mycobacteria.