ABSTRACT
There were already over 100 antibiotics commercially available for therapy when authors started our screening program for new antibiotics. Opportunistic infection and the appearance of clinical isolates resistant to a variety of antibiotics, however, remained great problems in therapy. Pure cultures of potential and interesting microorganisms were screened on several kinds of media differing in carbon, nitrogen source, and other constituents and buffer for a pH range. In 1977, Micromonospora olivasterospora, which was named later, isolated from soil in Hiroshima, was found to produce several mixtures of new antibiotics. The structure of astromicin was determined by proton magnetic resonance, carbon magnetic resonance, mass spectra and CD combined with chemical degradation. Proportional correlation between productivity and self-resistance to astromicin has been observed among the producing strains isolated. Special conditions such as preculture before proplast formation, composition of the regeneration medium, and regeneration conditions were required.
