ELECTRON MICROSCOPIC STUDIES ON ULTRATHIN SECTIONS OF SPORES OF CLOSTRIDIUM TETANI AND CLOSTRIDIUM HISTOLYTICUM, WITH SPECIAL REFERENCE TO SPORULATION AND SPORE GERMINATION PROCESS

Abstract

The mature spores of Clostridium tetani and Clostridium histolyticum were enveloped by the sporangium cell wall and exosporous sporangium cytoplasm, and, especially in Clostridium tetani, the exosporium of a characteristic nature was formed in the exosporous sporangium cytoplasm, enveloping the proper spore portion. The proper spore portion possessed the structures in the following order as observed from the outer side, (1) the outer spore coat of three layered structure, (2) the less dense intermediate space having the remains of the cytoplasm, (3) the inner spore coat, (4) the cortex, a relatively less dense portion, and (5) the dense core which is located in the center of the spore. The so-called nuclear elements of lower density is situated within the core.
In the initial stage of the sporulation process, the nuclear site, which is located correspondingly to the expected place of spore formation, was enlarged ; and the less dense bordering layer, which limited the spore portion from the sporangium cytoplasm, appeared, taking a part of the cytoplasm into the spore. Following this, at the outside of the bordering layer, the dense outer spore coat began to appear fragmentarily, gradually proceeding to envelop the whole spore. At about the same time, the formation of the core by means of the complex intermingling of the nuclear material with the cytoplasm in the spore portion was initiated. Also, the inner spore coat and cortex became distinct around the core. The other nuclear sites, except the one which was included in the sporulation process, became contracted and finally disappeared during the process.
The first indication of the spore germination process was the appearance of distinct nuclear elements, the movement of the nuclear elements to the interior of the spore, and the swelling of inner spore coat and cortex. Following this, the nuclear apparatus appeared in the nuclear elements which had been already turned to the nuclear sites. This is accompanied by the change in the characteristic compact spore cytoplasm into a spongy structure. On the other hand, the cell wall of newly germinated vegetative cells appeared as the inner spore coat and cortex disappeared. The cell wall was believed to originate from the membrane which enveloped the core.
Anomalous sporulation process and malformed spores were also described.