Which compound in the cell wall contributes to acid-fast staining of Mycobacterium tuberculosis?

Which compound in the cell wall contributes to acid-fast staining of Mycobacterium tuberculosis?

• A. Trehalose dimycolate
• B. Sulfatides
• C. Lipoarabinomannan
• D. Mycolic acid

Answer: (D)

Acid-fast staining hinges on a waxy, lipid-rich cell wall created by long-chain mycolic acids. This lipid barrier resists decolorization by acid-alcohol, so the red dye used in the stain remains trapped inside the cells, giving acid-fast organisms their characteristic appearance. The specific component responsible is mycolic acid, a very long–chain fatty acid integrated into the cell wall's mycolyl-arabinogalactan-peptidoglycan complex. Other listed lipids, like trehalose dimycolate, sulfatides, and lipoarabinomannan, contribute to virulence or cell-wall structure but do not alone confer the acid-fast property.

Acid-fast staining hinges on a waxy, lipid-rich cell wall created by long-chain mycolic acids. This lipid barrier resists decolorization by acid-alcohol, so the red dye used in the stain remains trapped inside the cells, giving acid-fast organisms their characteristic appearance. The specific component responsible is mycolic acid, a very long–chain fatty acid integrated into the cell wall's mycolyl-arabinogalactan-peptidoglycan complex. Other listed lipids, like trehalose dimycolate, sulfatides, and lipoarabinomannan, contribute to virulence or cell-wall structure but do not alone confer the acid-fast property.