Kanamycin A is a broad spectrum antibiotic isolated from a soil streptomyces (S. kanamyceticus). This aminoglycoside alters translation by prokaryotic ribosomes, resulting in bacterial cell death. In molecular biology, kanamycin A is used as a selective agent to isolate transformants that are expressing a kanamycin resistance gene, usually neomycin phosphotransferase (NptII/neo). This mode of selection is most commonly used in plant and mammalian biology.