Figure 2. Cytological assessment of the timecourse of sporulation.
(A) Samples were taken at the indicated times and stained with DAPI (4'-6' diamidino-2-phenylindole) by standard methods. Percentages of cells containing mature spores, tetranucleate cells, binucleate cells, and mononucleate cells are plotted (n=200). The final sporulation efficiency after more than 24 hours was 67%. (B) Samples were taken at the indicated times and subjected to sectioning, staining, and observation by electron microscopy. Because cell sections rather than entire cells were analyzed, percentages reflect relative rather than absolute frequencies of spores and lipid bodies. The curves represent the fraction of cell sections containing mature spores, the fraction containing immature spores (missing intact mature spore wall), the fraction of cell sections containing either of those two, and the fraction containing more than 3 "lipid bodies" (an ultrastructural term referring to an early progenitor of the spore wall).