STUDIES ON VALIDAMYCINS, NEW ANTIBIOTICS. II

Abstract

The fermentation conditions for the production of validamycin by Streptomyces hygroscopicus var. limoneus No. T-7545 were studied. Validamycins A and B showed no antimicrobial activity on agar media against bacteria, yeasts and fungi, but caused an abnormal branching at the tips of the hyphae of Pellicularia sasakii. Although they were inactive in vitro, validamycins A and B controlled the sheath blight of rice plants and the damping off of cucumber seedlings in green house tests. Validamycin A was effective against the sheath blight at a concentration of 30ppm. Both antibiotics showed low toxicity to plants, fishes and mice.