**Core Concept**
Chloramphenicol is a broad-spectrum antibiotic that inhibits protein synthesis in bacteria by binding to the 50S ribosomal subunit, thereby blocking the action of peptidyl transferase enzyme.

**Why the Correct Answer is Right**
Chloramphenicol binds to the 50S ribosomal subunit, which is crucial for peptide bond formation. This binding inhibits the action of peptidyl transferase enzyme, preventing the formation of peptide bonds between amino acids. As a result, protein synthesis is halted, and bacterial growth is inhibited. The 50S ribosomal subunit is the target of chloramphenicol, making it an effective antibacterial agent.

**Why Each Wrong Option is Incorrect**
* **Option A:** Incorrect because chloramphenicol does not work by inhibiting DNA replication or transcription. Its action is at the level of protein synthesis.
* **Option B:** Incorrect because chloramphenicol does not work by inhibiting cell wall synthesis, which is the mechanism of action of beta-lactam antibiotics like penicillin.
* **Option C:** Incorrect because chloramphenicol does not work by inhibiting fatty acid synthesis, which is the mechanism of action of some antibiotics like tetracyclines.

**Clinical Pearl / High-Yield Fact**
Chloramphenicol is a powerful antibacterial agent, but its use is limited due to its potential toxicity, including bone marrow suppression and gray baby syndrome in neonates.

**Correct Answer: D. Inhibits protein synthesis by binding to the 50S ribosomal subunit.**