Fig. 3.

Cross sections through Bacillus subtilis spores after rapid embedding in LR White (2.5 μl accelerator per ml monomer) and using different fixation protocols. Fixation was done with a final concentration of: A. 10% formaldehyde, 0.05% glutaraldehyde in 0.05 M Hepes buffer (pH 7.2) for 10 min at room temperature (PFA/GA 10′); B. 2.5% glutaraldehyde for 4 h at room temperature (GA 4 h); C. 10% formaldehyde, 0.05% glutaraldehyde in 0.05 M Hepes buffer (pH 7.2) for 5 min at room temperature followed by 2 min heating to 37 °C, 2 min heating from 37 °C to 50 °C and 6 min holding at 50 °C in a microwave oven (PFA/GA MW); D. 10% formaldehyde, 0.05% glutaraldehyde in 0.05 M Hepes buffer (pH 7.2) for 5 min at room temperature followed by 10 min at 50 °C in a water bath (PFA/GA ht). Bars = 100 nm.