Final answer:
Among the options given, aminoglycosides are the drugs that act against protein synthesis by binding to the 30S subunit of bacterial ribosomes. Beta-lactams, trimethoprim, and polymyxins do not target protein synthesis directly; they impact cell wall synthesis, folic acid metabolism, and cell membrane integrity respectively.
Step-by-step explanation:
Drugs that act against protein synthesis include several classes of compounds that target various processes in the protein synthesis pathway. Among the options provided, aminoglycosides are the drugs known to bind to the 30S subunit of bacterial ribosomes and interfere with protein synthesis. These drugs include streptomycin, gentamicin, neomycin, and kanamycin, which are broad-spectrum antibacterials. They work by impairing the proofreading ability of the ribosomal complex, leading to the production of faulty proteins that can disrupt the bacterial cytoplasmic membrane, ultimately killing the bacterial cells.
On the other hand, beta-lactams like penicillins and cephalosporins, inhibit the synthesis of peptidoglycan layer of bacterial cell walls rather than directly targeting protein synthesis. Trimethoprim interferes with bacterial folic acid metabolism and not with protein synthesis directly. Polymyxins disrupt the cell membrane of bacteria, not directly affecting the protein synthesis either.