[Comparative electron-microscopic study of 8 representatives of the genus Corynebacterium grown on solid nutrient...

After 18 hours of growth on selective serum-agar medium C diphtheriae cultures with different toxicogenic activity, and also diphtheroid and Hoffmann's baccillus cultures were removed, washed of the remnants of the nutrient medium and fixed under cold conditions by two combined methods (with glutaric aldehyde-osmic acid--uranyl acetate, and potassium permeanganate--uranyl acetate). The preparations were studied in ultrathin sections. It appeared that corynebacteria had during the stationary phase of development a general structural plan characteristic of Gram positive microorganisms and for all the corynebacterium genus. Cells of diphtheria toxicognic strains had signs of the accelerated (in comparison with other strains) rate of development; the principal mass of toxicogenic cells after 18 hours of growth had morphological signs of the stage of rest. The majority of cells whose toxicogenicity was inconstant had an extensive microcapsule which was also a characteristic element of the diphtheroid and Hoffmann's bacillus ultrastructure. The total thickness of the walls in the cells of toxicogenic strains and of the strains whose toxicogenicity was inconstant constituted 190-200 A; in nontoxicogenic strains, diphtheroid and Hoffmann's bacillus it was from 230 to 320 A. Surface structures of corynebacteria were differentiated better in the cells with toxicogenic activity. In the majority of cells of nontoxicogenic strains and also diphtheroid and Hoffmann's bacillus individual wall layers were differentiated with difficulty.