RESUMO
Cytomorphological and cultural characteristics of highly and low active collection strains of Streptomyces fradiae producing tylosin were studied. The strains were grown on agarized and liquid media. It was shown that unlike the low active strain, the highly active one was less sporogenic, the difference being more pronounced when tylosin was added to the agarized medium. When the strains were grown in the fermentation medium there were detected differences between them in the growth type and microcolony structure at the early stages of the fermentation process. During intensive synthesis of tylosin spheric structures were found to form near the hyphal surfaces. The phenomenon was previously observed in cultures producing other antibiotics. In the low active strain the structures were single while in the highly active strain they formed in large numbers.
