Nourseothricin sulfate is a complex of streptothricins C, D, E and F, isolated from Streptomyces noursei. Nourseothricin is structurally unrelated to other aminoglycosides with a glucosamine bearing a carbamoyl at the 4-hydroxy position linked to an atypical amino acid, streptolidine, via a β-glycoside linkage. The members of the complex differ in the length of the peptide side chain containing 1, 2, 3 or 4 ß-lysine residues, respectively. Nourseothricin is active against many prokaryotic and selected eukaryotic species, including yeasts, fungi, protozoa, insects and plants. Nourseothricin is inactivated by acetylation of the β-amino group of the β-lysine residue, conferred by the NAT-1 gene.