Umezawa, et al.¹⁾ had reported a new antibiotic kanamycin and the strain producing this antibiotic was assigned to a new species, Streptomyces kanamyceticus. This strain was isolated by the present authors from a soil sample taken at Nagano Prefecture. This strain was numbered as K-2J in Department of Antibiotics, National Institute of Helath and as Ka (by the Japanese syllabary)-2J in Department of Bacteriology, Faculty of Medicine, Shinshu University. After the usefulness of kanamycin had been widely known, the present authors needed to study the origin of the soil more in detail. K-2J strain of National Institute of Health and Ka-2J of Shinshu University were recorded to have been isolated from a soil sample taken at Tobira Hot Spring Place in Nagano Prefecture. One of the present authors, Tazaki, Department of Bacteriology, Shinshu University, had also kept another strain which was numbered as K-2J in his laboratory, and which was recorded to have been isolated from a soil taken at Nagoya. Reconfirmation of record revealed that the kanamycin-producing strain was his strain of Ka-2J, but not his strain of K-2J. Thus, the origin of the kanamycin-producing strain was determined to be the soil of Tobira Hot Spring Place in Nagano Prefecture.

The strain K-2J (the present authors adopt the strain number of K-2J of National Institute of Health hereafter), S. kanamyceticus, showed originally yellow colored growth as indicated in the previous paper, but white colonies were frequently found on agar slant or plates of Czapek’s agar or Krainsky’s glucose asparagine agar. These white colonies were not contaminants. The study of mutants which are frequently obtained must be helpful for detailed characterization of the kanamycin producing strain. This kind of study is also helpful for improving the strain refering to its productivity of kanamycin and would contribute to the knowlege of variation in a species of S. kanamyceticus. In this paper, the authors describe several types of mutants of this species with reference to their productivity of the antibiotics.