Influence of A-factor on the ultrastructure of the A-factor deficient mutant of Streptomyces griseus.

The fine structure of the A-factor deficient mutant strain of Streptomyces griseus grown in the absence or in the presence of this factor was studied by transmission electron microscopy. The submerged 96 h culture grown in the presence of the A-factor was characterized by the formation of a large amount of spores accompanied by mycelium disintegration. A number of essential ultrastructural changes were observed in the mycelium in the course of development and streptomycin biosynthesis after the A-factor addition. Thus, the cell wall was transformed in another manner at various developmental stages. For a long time the associated ribosomes were preserved. The number of intracytoplasmic membrane structures increased. New, unusual organelles appeared which consisted of parallel cylindrical structures. The possible nature of these organelles is discussed.