Neomycin is an aminoglycoside antibiotic extracted from Streptomyces fradiae. Neomycin has a broad spectrum of activity against both gram-positive and gram-negative bacteria. This antibiotic is a combination of neomycin B (framycetin) and its epimer neomycin C.
Neomycin is usually used as a selective marker in gene replication, therefore it is used in culture media to select clones that have the neomycin resistance gene inserted into their genome.