Blasticidin S hydrochloride is a salt of blasticidin S, an amphoteric nucleoside produced by several species of Streptomyces, first reported in the late 1950s. Blasticidin S hydrochloride was originally isolated by acetone precipitation. For historical reasons only the salt has been routinely available to researchers. Both the salt and free base are freely water soluble. Blasticidin S is an antifungal agent with particularly potent activity against the rice pathogen, Piricularia oryzae, for which it was used commercially for some time in Japan. Blasticidin S inhibits protein synthesis and is active against bacteria, tumor cell lines and nematodes. More recently, blasticidin S has been used as a marker for strain manipulations.