Antibiotics and modes of action

1) Chloramphenicol binds to 23S rRNA of 50S subunit in bacterial ribosome to block the action of peptidyl transferase enzyme and thus inhibit the peptide bond formation and protein synthesis.

The antibiotic would block the attachment of the mRNA to the ribosome

2) Tetracycline binds to the bacterial 30S ribosome in reversible way and block the entry of aminoacylated t-RNA at A site (acceptor site) and prevent addition of amino acids to the elongating peptide chain, thus inhibits the protein synthesis.

The antibiotic would prevent the second amino acid from being added

3) Streptomycin binds to the 16S rRNA of 30S subunit in bacterial ribosome an interfere the binding of formyl methinine t-RNA to the 30S subunit which leads to misreading of codon and inhibition of protein synthesis and thus results in microbial death.

The antibiotic would cause the mRNA to be misaligned at the mRNA tunnel