Question

The following is TRUE for Mycoplasma EXCEPT:

• A. Multiply by binary fission
• B. Are sensitive to the beta-lactam group of antibiotics
• C. Can grow in cell-free culture media
• D. Require sterols for growth

Hint:

Mycoplasma has no cell wall, so beta-lactam antibiotics, which target cell wall synthesis, cannot act on it.

Answer 1

The Correct Option is B

Step 1: Recall what makes Mycoplasma unique among bacteria.
Mycoplasma are the smallest free-living organisms capable of self-replication. Their single defining feature is that they completely lack a rigid cell wall, unlike almost all other bacteria.

Step 2: Check option 1, binary fission.
Like other bacteria, Mycoplasma reproduce by binary fission, splitting one cell into two. This IS true.

Step 3: Check option 3, cell-free culture media.
Mycoplasma can be grown on special cell-free artificial media, such as PPLO (pleuropneumonia-like organism) agar enriched with serum, unlike obligate intracellular organisms such as Chlamydia and viruses. This IS true.

Step 4: Check option 4, requirement for sterols.
Because Mycoplasma has no cell wall, its plasma membrane must be reinforced with cholesterol (a sterol) for stability, so growth media for Mycoplasma must supply sterols, usually from added serum. This IS true.

Step 5: Check option 2, sensitivity to beta-lactams.
Beta-lactam antibiotics (penicillins, cephalosporins) work by blocking the enzymes that build peptidoglycan, the material that makes up a bacterial cell wall. Since Mycoplasma has no cell wall at all, there is no peptidoglycan for these drugs to attack, so Mycoplasma is inherently resistant to the entire beta-lactam group. Effective drugs against Mycoplasma instead target protein or DNA synthesis, such as macrolides, tetracyclines or fluoroquinolones. This statement is FALSE, making it the exception.

Step 6: Final answer.
The statement that is not true for Mycoplasma is that it is sensitive to beta-lactam antibiotics.
\[ \boxed{\text{Are sensitive to the beta-lactam group of antibiotics}} \]