A Membrane Filter Mounting Method and Spore Stain for Saccharomyces

Sporulated yeast cells seeded on 5 × 10 mm rectangles of ultrathin Millipore membrane filter are stained through the membrane with Ziehl's carbol-fuchsins. This is followed by 0.1% aqueous ruthenium red which both destains and counterstains. The preparations are made permanent with a water mounting medium. By a modification of the procedure microcolonies can be grown on the membranes, stained, and permanently mounted.