[Morphofunctional changes in the mycelium of active and inactive variants of Actinomyces parvullus during growth and biosynthesis of actinomycin D].

The structure and function of the mycelium were studied with active and inactive variants of Actinomyces parvillus producing actinomycin D. Changes in the morphology were found in the hyphae of the active variant during its growth and production of the antibiotic: the cell wall became first thicker in the course of growth and then thinner with aging; the ribosomes aggregated prior to intensive synthesis of actinomycin but disintegrated later into fine-granular regions; electron-trasnparent bodies of irregular shape appeared in the cytoplasm, and their content was liberated into the medium upon lysis of the cytoplasmic membrane and cell wall. These changes were not detected in the mycelium of the inactive variant. The disintegrated mycelium of the active variant was studied by differential ultracentrifugation, and the electron-transparent bodies in the cells were presumed to be of the antibiotic nature. A capsule is formed around the hyphae at the beginning of the antibiotic synthesis, and thickens in the course of growth. Intrahyphal hyphae are very often encountered in the culture. Possible mechanisms protecting cells in unfavourable conditions are discussed.