Organisms such as M. tuberculosis do not gram stain well because:
their waxy cell wall contains mycolic acid
Mycobacterium tuberculosis does not gram stain well because of its unique cell wall composition. The cell wall of M. tuberculosis is rich in lipids, including mycolic acid, which makes the cell wall waxy and hydrophobic. This property makes it difficult for the crystal violet stain and iodine mordant to penetrate the cell wall and be retained during the decolorization step with alcohol or acetone. As a result, the cells of M. tuberculosis appear as acid-fast under the microscope after counter-staining with fuchsin. The acid-fast staining property of M. tuberculosis allows it to be detected using the Ziehl-Neelsen staining technique. It is important to note that the acid-fast staining is not specific to M. tuberculosis and can also be observed in other pathogenic bacteria such as Nocardia and some species of Rhodococcus.
More Answers:
[next_post_link]