The mycological properties and antibiotic activity of strain No. B5477, isolated from a soil sample collected in Nishinomiya, Hyogo Prefecture, were investigated. This strain forms spiral sporophores, spiny spores, and gray aerial mycelium. The culture is non-chromogenic. Strain No. B5477 was compared with known species and identified as a strain of Streptomyces fungicidicus Okami et al. 1954¹⁾. During the course of selecting a strain with high potency, a yellow mutant with yellowish aerial mycelium was obtained and its properties were investigated.
Streptomyces fungicidicus No. B 5477 produces a new antibiotic, enduracidin, with a strong antibiotic activity against Gram-positive bacteria. Acid-fast bacteria and phytopathogenic bacteria are also inhibited. Enduracidin shows no cross resistance with the known antibiotics examined. It is more active in a basic medium and therefore is a basic antibiotic. The antibiotic activity of enduracidin was not affected by horse serum in the assay medium. Its diffusibility was less than that of the other antibiotics examined. The antibiotic activity of enduracidin was assayed by the paper disc method using Sarcina variabilis IFO 3067 as the test organism. Enduracidin was produced mainly in the mycelium. The fermentation conditions for production of the antibiotic were investigated.