A new antimicrobial agent, coumermycin**, has been isolated from fermentation beers of a strain of Streptomyces named Streptomyces rishiriensis nov. sp. The strain, No. 404Y3 in our culture collection, was isolated from a sample of soil collected in Rishiri Island, Hokkaido, Japan. The antibiotic is a white acidic substance and relates to novobiocin^7–13) in some respects of biological and chemical properties. The chromatographic and degradation studies on the antibiotic revealed the fact that the original culture produces several components which seemed to be closely related each other. Therefore, studies were undertaken to obtain a single component having the most potent biological activity which has been designated coumermycin A₁.

This paper deals with the producing organism, production, isolation as well as biological and physico-chemical properties of coumermycin A₁. The structural studies on coumermycin A₁, C₅₅H₅₉N₅O₂₀, will be reported in companion papers¹⁾.