Fluorescent staining of fungal nuclei with a benzimidazol derivative

A direct staining procedure is described for fluorescence microscopy of fungal nuclei, chromosomes and mitochondria. The fluorochrome is a benzimidazol derivative (33258 Hoechst) known to bind selectively to deoxyribonucleic acid at neutral pH. The advantages of 33258 Hoechst relative to Feulgen compounds used previously to stain these structures include a greater intensity of fluorescence, the absence of fading or rapid quenching of the fluorescence, and the omission of acid hydrolysis from the procedure for removal of ribonucleic acid. 33258 Hoechst has been evaluated as a nuclear stain with a yeast (Saccharomyces cerevisiae) and a filamentous fungus (Agaricus bisporus) and appears to penetrate easily vegetative cells and spores of both fungi.