Which of the following antibiotics inhibits the 50S ribosomal subunit to disrupt protein synthesis?

Chloramphenicol is the antibiotic that specifically inhibits the 50S ribosomal subunit, thereby disrupting protein synthesis in bacteria. This antibiotic binds to the 50S subunit and interferes with peptide bond formation during translation, which is a critical step in protein synthesis. As a result, this leads to the inhibition of bacterial growth and replication.

In contrast, the other classes of antibiotics mentioned do not act on the 50S ribosomal subunit. Aminoglycosides, for example, target the 30S subunit, causing misreading of mRNA and ultimately inhibiting protein synthesis. Tetracyclines also act on the 30S ribosomal subunit, preventing the attachment of aminoacyl-tRNA to the mRNA-ribosome complex, which blocks the addition of new amino acids to the growing polypeptide chain. Penicillins, on the other hand, are beta-lactam antibiotics that interfere with bacterial cell wall synthesis rather than protein synthesis.

Therefore, chloramphenicol is uniquely recognized for its mechanism of action on the 50S ribosomal subunit, making it the correct answer to the question regarding the disruption of protein synthesis through this specific target.