Kanamycin inhibits bacterial protein synthesis by binding 70S ribosomes resulting in dysfunctional translation of mRNA commonly used to select for cosmid vectors. Effective against both gram (-) and gram (+) bacteria.

Chloramphenicol inhibits bacterial protein synthesis by binding 50S ribosomal subunit. Commonly used for the amplification of vectors in gram (-) bacteria. Effective against both gram (-) and gram (+) bacteria and some mycobacteria.

Tetracycline inhibits bacterial protein synthesis by binding the 30S ribosomal subunit. Effective against both gram (-) and gram (+) bacteria.

Ampicillin inhibits bacterial cell wall synthesis. Commonly used to select for ampicillin resistant plasmid bearing strains of bacteria. Effective against both gram (-) and gram (+) bacteria.