Improved contrast by a simplified post-staining procedure for ultrathin sections of resin-embedded bacterial cells: Application of ruthenium red

High contrast can be obtained in ultrathin sections of bacterial cells embedded in the low-temperature resin Lowieryl by post-staining of the sections on an aqueous ruthenium red solution. Post-staining with lead citrate can be omitted. Combination with post-staining with uranyl acetate results in further improvement of contrast. This is shown for Gram-positive, Gram-negative, and methanogenic bacteria. Improved visibility is demonstrated for wall layers including slime and capsule, cytoplasmic membrane, nucleoid, envelope of PHB inclusion bodies, polyphosphate, and intracellular defective bacteriophages. The procedure is suited as post-staining for immunocytochemical analyses.