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The nature of the fine structure of the spores of fusidic acid-producing organism changed with an increase in the antibiotic activity of its strains. Impairments in the structure of the cell coating were observed. The surface layers of the spore wall became labile, they were capable of separating, destructive impairment in the electron solid structures were detected in the spore cytoplasm, such impairments resulted in autolysis of extended areas. The lability of the surface layers of the spore wall promoted contacts between the spore cell coatings. The increased adhesive properties of the spore coatings resulted in formation of the spore "heads" typical of sporulation in highly active strains. The latter were characterized by a marked increase in the number of the spores filled with lipids and devoid of the main cell organelles and having a changed structure of the spore wall. This explained the marked decrease in the viability of the conidia of the highly active strains of the organism producing fusidic acid.

The physiological and morphofunctional properties of the polyene-sensitive and resistant mutants of fungus producing fusidic acid were studied comparatively. The highly active nystatin resistant mutant was characterized by the decreased growth rates, lowered sporulation levels, retarded synthesis of nucleic acids and protein, lower respiration activity and higher mycelium lipid contents. The ultrastructural investigation of the polyene-resistant strain revealed the presence of lower numbers of ribosomes, membrane structures and mitochondria. Destructive changes in mitochondria and lipid masses in the hyphal cytoplasm were also observed.