Ready-to-use 10 mg/ml Tetracycline Hydrochloride Solution|Tetracycline inhibits bacterial protein synthesis by binding the 30S ribosomal subunit. Tetracycline is effective against both Gram (-) and Gram (+) bacteria. Resistance to tetracycline is conferred by the tet gene product that alters the bacterial cell membrane and transport of the antibiotic into the cell.