Which statement best describes acid-fast Mycobacteria?

Which statement best describes acid-fast Mycobacteria?

• A. Their cell walls have high lipid content
• B. They lack lipids
• C. They have thick peptidoglycan only
• D. They have no cell wall

Answer: (A)

Acid-fast Mycobacteria are defined by a cell wall that is exceptionally rich in lipids, especially long-chain mycolic acids, giving it a waxy, hydrophobic character. This high lipid content is what makes the wall resistant to decolorization by acid-alcohol during acid-fast staining, allowing the stain to be retained and the organisms to appear bright after staining. That lipid-rich barrier also explains why these bacteria grow slowly and are relatively resistant to many chemicals. So, the best description is that their cell walls have high lipid content. They do contain lipids, so lacking lipids is incorrect; they have more than just thick peptidoglycan, since the wall also includes arabinogalactan linked to mycolic acids; and they do have a cell wall, so the notion of no cell wall is false.

Acid-fast Mycobacteria are defined by a cell wall that is exceptionally rich in lipids, especially long-chain mycolic acids, giving it a waxy, hydrophobic character. This high lipid content is what makes the wall resistant to decolorization by acid-alcohol during acid-fast staining, allowing the stain to be retained and the organisms to appear bright after staining. That lipid-rich barrier also explains why these bacteria grow slowly and are relatively resistant to many chemicals. So, the best description is that their cell walls have high lipid content. They do contain lipids, so lacking lipids is incorrect; they have more than just thick peptidoglycan, since the wall also includes arabinogalactan linked to mycolic acids; and they do have a cell wall, so the notion of no cell wall is false.