The fine structure of frozen-etched bacillus cereus spores

Summary The fine structure of Bacillus cereus spores was studied using the freeze-etching technique and compared with that already described in chemically fixed cells. Although the basic structures did not appear different, the freeze-etching technique permitted the examination of membrane surfaces and their involvement in sporulation. In this respect, some membranes were found to be covered with small 120 Å particles believed to represent multi-enzyme complexes, while other membranes appeared relatively smooth.One feature revealed by the freeze-etching technique and not demonstrated in chemically fixed cells, was the presence of relatively large (500 Å) vesicular structures. In many instances these vesicles were closely associated with different layers or membranes in the developing spore. While the role of these vesicular structures is as yet undetermined, their possible connection with the lytic process which liberates the spore from the sporangium, is discussed.