Question

Which one of the following is not true of mycoplasmas?

• A. They do not have cell wall
• B. They cannot be cultured in laboratory
• C. Lipoglycans in mycoplasma help in attachment to cell surface receptors of animal cells
• D. They do not stain gram positively

Hint:

Mycoplasmas are the smallest free-living self-replicating organisms known, and they require pre-formed sterols in their growth media for membrane stability.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Mycoplasmas are unique, ultra-small, pleomorphic bacteria classified within the class Mollicutes.

Step 2: Detailed Explanation:
- (A) is true because mycoplasmas completely lack a peptidoglycan cell wall. This makes them pleomorphic (variable in shape) and naturally resistant to antibiotics like penicillin that target cell wall synthesis.
- (C) is true because they contain specialized membrane lipoglycans and proteins that facilitate adherence to host cell surface receptors.
- (D) is true because, lacking a cell wall, they do not retain the primary crystal violet dye during Gram staining, typically staining gram-negative.
- (B) is false because, although they are fastidious and require complex growth media supplemented with sterols (like cholesterol), many mycoplasma species can be cultured in the laboratory on specialized artificial media.

Step 3: Final Answer:
The statement that mycoplasmas cannot be cultured in the laboratory is not true.