Which structural characteristic of bacterial ribosomes primarily enables selective toxicity of many protein synthesis inhibitors?

• A. Bacterial ribosomes exist in a membrane-bound organelle and therefore are isolated from host ribosomes, allowing drugs to target them without affecting host translation machinery in the cytosol, which explains selective toxicity.
• B. They operate at a different pH optimum than eukaryotic ribosomes and drugs selectively alter local pH around bacterial ribosomes to block protein synthesis while leaving human ribosomes unaffected.
• C. They are 70S ribosomes made of distinct 30S and 50S subunits with rRNA and protein sequences sufficiently different from eukaryotic 80S ribosomes.
• D. Bacterial ribosomes are composed of DNA rather than RNA and protein, a fundamental difference that antimicrobials exploit to inhibit bacterial protein synthesis without harming eukaryotic cells.

Answer: (C)