[Extracellular material of some representatives of the genus Corynebacterium (the electron microscopic aspect)]

At the active developmental phases (up to 2 days) cells of toxigenic and nontoxigenic corynebacteria form extracellular vesicle-like material of two types which can be revealed both on whole cells set off by metal and stained negatively, and in ultrathin sections. Extracellular material of the first type is a derivative of an extensive membranous coat of corynebacteria and is formed as a result of its fragmentation. Vesicles of this type are devoid of electron microscope-dense content, have no tendency to coalescence, and fail to promote cell agglutination. Extracellular material of the second type is primarily formed by local thickening of the surface wall layer limited by its external dense layer and the main massif. These thickenings are filled with a microgranular substance of medium electron optic density; after accumulation this substance is released into the external environment. Vesicles of this type promote cell agglutination. Undoubtedly, extracellular material of the second type has a direct relation to the cell metabolic processes. Extracellular material of both types is encountered in all the cultures grown both on hard and in fluid nutrient media. However, in the latter case the process is apparently much more intensive. There is strict correlation between the morphology of the extracellular material and strain signs of the culture, although material of the second type is found to prevail in the cells from cultures possessing toxigenic activity.