Flow cytometry as a tool to discriminate respiratory-competent and respiratory-deficient yeast cells.

The cationic lipophilic dye Rhodamine 123 (Rh123) is selectively enriched in mitochondria in a membrane potential-dependent manner. Application of drugs which interfere with the electron flow of the respiratory chain lead to a severe reduction of mitochondrial dye uptake. In this communication we show that the same effect is observed after Rh123-staining of respiratory-deficient yeast mutants. Based on this observation we used flow cytometry to discriminate respiratory-competent and respiratory-deficient yeast cells. Combined with a cell sorter we were able to selectively enrich respiring and non-respiring yeast cells, respectively, from a mixture of cells.