**Question:** TRUE about mycoplasma is -

A. It is a gram-negative bacterium
B. It is a virus
C. It is a parasitic fungus
D. It is a protozoan parasite

**Correct Answer:** A. It is a gram-negative bacterium

**Core Concept**
Mycoplasma is a group of small, simple, and unique bacteria that belong to the class Mollicutes. They are the smallest known free-living true bacteria, lacking a cell wall and exhibiting a unique mode of cell division. As a result, they are often difficult to culture and identify in the laboratory.

**Why the Correct Answer is Right**
Mycoplasma is a gram-negative bacterium because it possesses a thin peptidoglycan layer beneath its plasma membrane, which stains red during Gram staining. This distinguishes them from gram-positive bacteria (having a thick peptidoglycan layer) and gram-positive fungi (which do not contain peptidoglycan at all).

**Why Each Wrong Option is Incorrect**

B. It is a virus: Mycoplasma is a bacterium, not a virus. Viruses are even smaller and lack cellular structures like DNA replication machinery, ribosomes, and membrane-bound organelles.

C. It is a parasitic fungus: Mycoplasma is a bacterium, not a fungus. Fungi are eukaryotic and possess cell walls with glucan components, a hallmark that is absent in Mycoplasma.

D. It is a protozoan parasite: Mycoplasma is a bacterium, not a protozoan. Protozoa are eukaryotic, have a single nucleus, and exhibit various shapes and life cycles that differ from Mycoplasma.

**Clinical Pearl**
Understanding the classification of microorganisms, including bacteria, viruses, fungi, and protozoa, is essential for medical professionals. Correct classification aids in appropriate laboratory diagnosis, treatment, and infection control strategies.