Fate of the Escherichia coli capsule during embedding procedures for electron microscopical studies.

The effect of the preparation steps of the TEM embedding procedure on the preservation of the Escherichia coli capsule was studied light microscopically. Electron microscopical micrographs did not distinctly reveal capsules whereas simultaneously performed India ink assays clearly revealed predominant capsules both on viable and on chemically fixed bacteria. It is clearly shown that dehydration does not cause extraction or collapse of capsular material to an extent that would explain the invisibility of the capsule on the electron microscopical level, as has hitherto been supposed.