116 PHYSIOLOGY OF YEASTS (Continued) 



wort to which dextrose had been added and others to which alcohol 

 had been added. 



The recent investigations of Saito 1 have furnished an explanation 

 of some of these facts and given information with regard to the for- 

 mation of ascospores which have been overlooked up to the present 

 time. Certain yeasts when placed in an environment with little food 

 do not contain certain necessary chemical substances which vary with 

 the yeast. For Zygosaccharomyces mandshuricus which has been the 

 special object of Saito's investigations, these substances are dextrose, 

 levulose, galactose, sorbose, raffinose, mannite, dulcite, sorbite and 

 glycerol. These substances seem to exercise a stimulating effect on 

 the sporogenic function. There seemed to be a mioimum concentration 

 for each of these compounds for sporulation. For example, the mini- 

 mum concentration of dextrose and levulose for Zygosaccharomyces 

 mandshuricus was between 0.125 and 0.25 per cent; for galactose, 

 raffinose, and glycerol between 0.25 and 0.50 per cent, and for sor- 

 bose and dulcite between 0.5 and 1 per cent. The addition of small 

 amounts of potassium phosphate and peptone exercised a favorable 

 action on sporulation in Zygosaccharomyces mandshuricus. The salts 

 of sodium, potassium, magnesium and carbon had a favorable action. 



Some substances, such as beer wort to which gelatin had been 

 added and decoction of koji, had a stronger action on the produc- 

 tion of ascs than the carbohydrates. Indeed, the action of beer wort 

 and decoction of koji caused a large number of ascs, but among them 

 were some with no ascospores. These various substances seem, then, 

 to have a specific action not only on the production of ascs but also 

 on the formation of ascospores and their maturation. 



Aside from substances which stimulate the formation of asco- 

 spores, there are substances which, in a marked manner, retard sporu- 

 lation. The salts of ammonia have such an action and when yeasts 

 are placed in certain concentrations of these salts, although all other 

 factors are favorable for sporulation, they do not sporulate. In gen- 

 eral it seems that those yeasts in which the asc is preceded by a sexual 

 process sporulate under more complex conditions than those which are 

 parthenogenetic. 



Sartory 2 has noticed a symbiosis between a yeast and bacterium. 

 The yeast sporulated only in association with the bacterium. Zetlin 3 



1 Saito, K. Untersuchungen iiber die chemischen Bedingungen fur die Ent- 

 wicklung der Fortpflanzorgane beinieigen Hefen. J. College of Sci. Imperial Univ. 

 Tokyo, 39, 1916. 



2 Sartory, A. Sporulation d'une levure sous Pinfluence d'une bacterie. Comp. 

 Rend. Soc. Biol. 72, 1912. 



3 Zetlin, Sophie. Influence of previous nourishment upon spore formation 

 in yeast. Chemical Abstracts, 8 (1914), 3807. 



