Kanamycin inhibits bacterial protein synthesis by binding 70S ribosomes resulting in dysfunctional translation of mRNA. Kanamycin is effective against both Gram (-) and Gram (+) bacteria. Resistance to kanamycin is conferred by an aminoglycoside phosphotransferase that modifies the antibiotic, preventing its interaction with ribosomes. Kanamycin is commonly used to select for cosmid vectors.