Which organism has a waxy cell wall rich in mycolic acids, making it relatively resistant to dehydration and some antibiotics?

Which organism has a waxy cell wall rich in mycolic acids, making it relatively resistant to dehydration and some antibiotics?

• A. Escherichia coli
• B. Staphylococcus aureus
• C. Mycobacterium tuberculosis
• D. Streptococcus pyogenes

Answer: (C)

A waxy, lipid-rich cell wall full of mycolic acids changes how a bacterium interacts with its environment by making the wall less permeable. This reduces drying out and also blocks many antibiotics that rely on penetrating the cell wall, helping the organism survive harsher conditions and some treatments. Mycobacterium tuberculosis is the classic example of this feature, which is why it’s described as having a waxy, mycolic acid–rich envelope. Because of this lipid-rich barrier, these bacteria are also identified by acid-fast staining, since the waxy wall retains certain stains. The other bacteria listed lack this specific mycolic acid–rich envelope. They have different wall structures (Gram-positive thick peptidoglycan or Gram-negative membranes) and do not exhibit the same level of dehydration resistance or this particular permeability profile.

A waxy, lipid-rich cell wall full of mycolic acids changes how a bacterium interacts with its environment by making the wall less permeable. This reduces drying out and also blocks many antibiotics that rely on penetrating the cell wall, helping the organism survive harsher conditions and some treatments. Mycobacterium tuberculosis is the classic example of this feature, which is why it’s described as having a waxy, mycolic acid–rich envelope. Because of this lipid-rich barrier, these bacteria are also identified by acid-fast staining, since the waxy wall retains certain stains.

The other bacteria listed lack this specific mycolic acid–rich envelope. They have different wall structures (Gram-positive thick peptidoglycan or Gram-negative membranes) and do not exhibit the same level of dehydration resistance or this particular permeability profile.