SPORULATION 3-2 



vation" conditions essential to sporulation involved primarily the 

 sugars in the substrate rather than other components. Welten (1914) 

 challenged the view that starvation was essential to sporulation. He 

 found that on prune extract agar, yeasts sporulated well. He even 

 doubted the necessity for oxygen, since in his experiments colonies 

 imbedded in the agar sporulated as well as those on the surface. He 

 found that yeasts grown in pear extract or beer wort did not sporu- 

 late so well as those grown on prune extract agar, but sporulation 

 occurred when the washed yeast grown on pnme extract was placed 

 on glass plates, filter paper, or sterile washed agar slopes, if a drop 

 of prune extract were added. If no prune extract were added, no 

 spores were produced. Grorodkowa's and Welten' s work proved that 

 starvation alone is not the complete explanation of the phenonenon. 

 Welten showed further that acidity of the medium in which sporulation 

 occurred was important, no spores occurring in an alkaline milieu. 

 Welten also found that more spores were produced in concentrated 

 than in dilute prune extract, also that a small amount of MgS04 aided 

 sporulation. Young cells were not essential; those 3-4 days old 

 sporulated better than those 1-2 days old. 



Baltatu (1939) found that spores were produced by mycodermas 

 in grape juice but usually germinated immediately, so that they could 

 be detected only by periodic examination of the culture. The addition 

 of very small amounts of acetic acid and grape juice to the water in 

 which the gypsum blocks were placed increased sporulation. 



Mrak, Phaff and Douglas (1942) discovered that many yeast sporu- 

 lated well on slopes of an agar medium containing a mixture of vege- 

 table (cucumber, beet, potato and carrot) extracts. This is clearly 

 a medium containing only a small amount of sugar, which is probably 

 soon exhausted to about the concentration of Gorodkowa's. 



Nickerson and Thimann (1942) found that conjugation and sporu- 

 lation occurred more abundantly in a Zygosaccharomyces when many 

 dead cells were present and postulated some stimulating substance 

 derived from the dead cells. Maneval (1942) found that sporulation 

 occurred in Saccharomyces on the outside of the compressed yeast 

 cakes. Nickerson and Thimann also discovered that an extract from 

 Aspergillus increased conjugation and sporulation, and later (1943) 

 suggested that riboflavin and sodium glutarate were the substances 

 in the extract responsible for the stimulation. 



The general conclusions from these data are that a specific pre- 

 sporulation nutrient is essential to abundant sporulation. If this nu- 

 trient is satisfactory and the sugar content of the medium low enough, 

 spoinilation may occur even on the agar slant, as in Gorodkowa's or 

 Mrak's media. Generally, the yeast should be removed from the 

 substrate, especially if its sugar content is high, and placed on gyp- 

 sum. The water saturating the gypsum slant should be acid and 



