Homomycin¹⁾, an antibiotic specifically active against bovine and human tubercle bacilli, has been found in the course of screening antituberculous antibiotics using bovine tubercle bacillus BCG as a test organism²⁾. The antibiotic has been obtained from culture filtrates of hitherto undescribed streptomycete, Streptomyces noboritoensis, which was isolated from a soil sample collected at Inada-noborito, Kawasaki City, Kanagawa Prefecture. It is almost nontoxic for mice and showed some therapeutic effect on experimental tuberculosis of mice.

Homomycin has been prepared as its purified powder as well as its crystalline 2, 4-dinitrophenylhydrazone. The analytical data and molecular weights of those indicated the molecular formula to be C₂₃H₂₉NO₁₂. The comparative studies with the similar antibiotic, hygromycin³⁾ indicated both were identical and the formula of hygromycin reported as C₂₅H₃₃NO₁₂ should be corrected*. The taxonomic studies showed St. noboritoensis belonging to the chromogenic type, differs distinctly from St. hygroscopicus, the hygromycin-producing strain. St. noboritoensis simultaneously produces an antibiotic, blastomycin**, specifically active against plant pathogenic fungus, Piricularia oryzae, and a basic antibiotic active against gram-positive bacteria in certain condition of cultivation.

The present paper deals with taxonomic studies of St. noboritoensis, isolation and properties of homomycin as well as the identity with hygromycin.