Novel polyether antibiotics X-14868A, B, C, and D produced by a Nocardia. Discovery, fermentation, biological as well as ionophore properties and taxonomy of the producing culture.

Polyether antibiotics are a large class of microbial secondary metabolites generally produced by soil actinomycetes of the genus Streptomyces'). Intensive search for new polyether antibiotics has in recent years revealed that other genera of streptomycetes also produce these antibiotics. Laidlomycin is produced by Streptoverticillum eurocidium'). Cationomycin'), antibiotics CP-47,433 and CP-47,4344) as well as CP-51,5323) are produced by strains of Actinomadura. Antibiotic CP-44,161 was isolated from the fermentation broth of a Dactylosporangium culture'). In this paper, we report the discovery of a novel polyether antibiotic complex produced by a hitherto undescribed Nocardia, strain X-14868. Nocardia X-14868 produces a complex of antibiotics with X-14868A the major component. A second component, X-14868B, originally thought to be elaborated directly by the producing organism, was later found to be an artifact chemically derived from X-14868A during the isolation work-up process. Other minor components that have been isolated from the culture broth are antibiotic X-14868C and X-14868D. The structure of each of these antibiotics shown in Fig. I was determined by X-ray crystallographic analysis'). This report is concerned with the taxonomy of the antibiotic producing