A procedure for the study by scanning electron microscopy of flocculating cells of the fission yeast Schizosaccharomyces pombe

We have investigated a variety of preparative and dehydrating technics in order to examine, by scanning electron microscopy, the cell surface morphology of the fission yeast Schizosaccharomyces pombe, during asexual and sexual flocculation. We found that the loss of the flocculum material surrounding the cell wall was a problem common to many technics. Observations ranged from cells that were covered in varying amounts of hairs, hairlike threads, or a mucilaginous coat to cells so devoid of surface material as to show only well-defined scar regions. The loss of flocculum material is particularly severe with different dehydrating procedures. The method found to provide the best preservation of the cell coat and to produce the most consistent results was double fixation by glutaraldehyde – osmium tetroxide followed by splash–freeze lyophilization. Flocs unfixed, fixed with glutaraldehyde, or stained with uranyl sulfate, and dehydrated followed by critical-point drying or solvent substitution were found to b...