Biosynthetic studies of amphotericins, candicidin and nystatin by means of mutation.

A novel mutant strain designated as Streptomyces nodosus, NDMC-034 was selected from the mutation of Streptomyces nodosus, IMRU 3694. This mutant was characterized by delayed sporulation, the incapability of producing the melanoid pigment either in the production medium or on YD agar containing 1% yeast extract and 1% dextrose, and the increased yield of amphotericin A as compared to its parent strain. In addition, the biosynthesis of amphotericin A by this mutant seems to be sensitive to temperature. When the incubation temperature was raised to 32 degrees C, the yield of amphotericin A was dramatically decreased; in contrast, the yield of amphotericin B was greatly increased as compared to that at 28 degrees C. Another unique mutant strain designated as Streptomyces griseus, YT-1 was selected from the mutation of Streptomyces griseus, IMRU 3570. It was characterized by the incapability of synthesizing candicidin and the delayed sporulation. All the mutants were auxanographed and characterized by the requirement for growth factor.