Observations on acid-fastness and respiration of germinating yeast ascospores

Germination of the ascospores of a strain of Saccharomyces cerevisiae Hansen was stimulated by fermentable carbon sources. Nitrogen sources alone had little or no stimulating effect on germination unless glucose was present, but peptone and casein hydrolysate were exceptions. Loss of acid-fastness proved to be a useful criterion of spore germination. Evidence was obtained that germination occurs anaerobically, but is not restricted by oxygen. It is concluded that the respiratory characteristics of the three main phases of the yeast life cycle differ in that growth can occur aerobically or anaerobically, sporulation is restricted to aerobic conditions, and spore germination is anaerobic.