[Electron microscopic study of Bacillus polymyxa in the developmental process and antibiotic formation].

The purpose of this work was to study growth of Bacillus polymyxa 153, biosynthesis of polymyxin by it, the formation of spores, and the fine structure of the cells. The antibiotic content was low in the cells and in the cultural broth during the first hours of growth and sharply increased later under the conditions of the medium ensuring the "vegetative" type of cultural growth. The cell wall reorganized, a periplasmic space appeared, and the membranous and mesosomal apparatus became more complicated in the cells actively synthesizing the antibiotic. The antibiotic content was higher in the cells belonging to the "spore" type of growth at the beginning of mass spore formation. Further cell development involved endospore differentiation; a complicated membranous apparatus did not appear, and biosynthesis of the antibiotic stopped.