A Study, with the High-Voltage Electron Microscope, of the Endospore and Life Cycle of Bacillus mycoides

Abstract

The structure of the endospore of B. mycoides and its development from spore to spore were studied with the high-voltage RCA electron microscope. The endospores, in their mother culture, vary considerably in appearance and, on that basis, may be classified in 3 groups The spore protoplasm appears homogeneous and is surrounded by 2 coats. Of the 2 coats, the inner one is the more rigid and the outer one the more elastic; both are shed upon germination. There is no evidence for the pre-existence, in the resting spore, of a 3d coat that beomes the wall of the germ cell. Spore germination is described in detail. The germ cell does not bear flagella and its protoplasm appears homogeneous. The lipoprotein inclusions which appear in the presporal stage were observed. The forespore appears homogeneous. The sporangial cytoplasm in the neighborhood of the spore is not more opaque to the electrons than that present in the "sterile" portion of the sporangium. Micrographs taken with the EMU are reproduced to show the advantage of using high voltage in the study of dense bodies such as the bacterial endospore.