Which statement about Mycoplasma best reflects its cell-wall status?

Which statement about Mycoplasma best reflects its cell-wall status?

• A. They lack a cell wall.
• B. They have a thick cell wall.
• C. They have a protective outer capsule.
• D. They are viruses.

Answer: (A)

The key point is that Mycoplasma lack a peptidoglycan cell wall. This absence makes them pleomorphic and means they don’t stain reliably with the Gram method, since there is no rigid wall to give a typical Gram-positive or Gram-negative appearance. It also explains why antibiotics that target cell-wall synthesis, like beta-lactams, are ineffective against them. Instead, they have a cytoplasmic membrane that contains sterols, which provides stability without a wall. So describing them as lacking a cell wall best captures their cell-envelope status. The other ideas—having a thick cell wall, a protective outer capsule, or being viruses—do not fit because Mycoplasma are bacteria and, by definition here, do not have peptidoglycan-based walls or viral properties.

The key point is that Mycoplasma lack a peptidoglycan cell wall. This absence makes them pleomorphic and means they don’t stain reliably with the Gram method, since there is no rigid wall to give a typical Gram-positive or Gram-negative appearance. It also explains why antibiotics that target cell-wall synthesis, like beta-lactams, are ineffective against them. Instead, they have a cytoplasmic membrane that contains sterols, which provides stability without a wall. So describing them as lacking a cell wall best captures their cell-envelope status. The other ideas—having a thick cell wall, a protective outer capsule, or being viruses—do not fit because Mycoplasma are bacteria and, by definition here, do not have peptidoglycan-based walls or viral properties.