Antibiotics that selectively inhibit bacterial growth exploit differences between bacterial and mammalian cells with respect to the ribosomes of the cells. A drug that would selectively inhibit bacterial RNA synthesis would target the prokaryotic ribosomes specifically,i.e. either target the 50S or 30S ribosomal subunits only and leave the eukaryotic ribosomes alone. Thus, the drug should be ribosomal unit specific and have specific ribosomal domain binding sites.