Because of the nature of their cell wall, acid-fast bacteria stain red after acid-fast staining. The genus Mycobacterium and the genus Nocardia are among the few bacteria possessing an acid-fast cell ...Because of the nature of their cell wall, acid-fast bacteria stain red after acid-fast staining. The genus Mycobacterium and the genus Nocardia are among the few bacteria possessing an acid-fast cell wall. The acid-fast cell wall consists of a thin, inner layer of peptidoglycan linked to a layer of arabinogalactin, which in turn is linked to an outer membrane containing mycolic acids and overlaid with a variety of polypeptides and glycolipids.