Question

Which genus of bacteria does NOT have a cell wall?

• A. \textit{Lactobacillus}
• B. \textit{Staphylococcus}
• C. \textit{Mycoplasma}
• D. \textit{Escherichia}

Hint:

Mycoplasma → no cell wall, pleomorphic in shape, resistant to penicillin.

Answer 1

The Correct Option is C

Step 1: Recall basic bacterial structure.
Most bacteria have a rigid cell wall made of peptidoglycan that provides structural strength and protection.

Step 2: Evaluate the options.
- (A) \textit{Lactobacillus} → Gram-positive bacteria with thick peptidoglycan cell walls.
- (B) \textit{Staphylococcus} → Gram-positive cocci, also with cell wall.
- (C) \textit{Mycoplasma} → Lacks a cell wall, bounded only by a plasma membrane. They are the smallest free-living bacteria and resistant to beta-lactam antibiotics because these drugs target cell wall synthesis.
- (D) \textit{Escherichia} (E. coli) → Gram-negative with thin peptidoglycan wall and outer membrane.

Step 3: Conclude.
The only bacteria without a cell wall are Mycoplasma. Final Answer: \[ \boxed{\text{(C) Mycoplasma}} \]