What is found on the mycobacterium cell wall that allows staining with carbol fuchsin to occur?

• A. Mycolic acid
• B. Lipopolysaccharide
• C. Chitin
• D. Peptidoglycan

Answer: (A)

Acid-fast staining depends on the waxy, lipid-rich mycobacterial cell wall, which is rich in mycolic acids. These long-chain fatty acids create a dense, hydrophobic barrier that the carbol fuchsin dye, with its phenol component, can penetrate and which remains bound to the wall even after acid-alcohol decolorization. That retention gives mycobacteria their characteristic red stain. The other components listed don’t confer this property: lipopolysaccharide is a feature of Gram-negative outer membranes and doesn’t provide acid-fastness; chitin is found in fungal cell walls; peptidoglycan is common in many bacteria but lacks the waxy, lipid-rich barrier that allows acid-fast retention.