CHAPTER XXXVII 

 CURRENT PROBLEMS ON YEASTS 



F. W. TANNER 



University of Illinois 



MORPHOLOGY AND ORIGIN OF YEASTS 



This subject has interested investigators since early times. The earlier literature 

 has been reviewed by Guilliermond and others who have prepared treatises on these 

 micro-organisms. The suggestion that yeasts represent a state of development of 

 higher molds seems to have been first made by Kiitzing in 1837. While the idea, ac- 

 cording to Fuchs/ has been widely accepted, good experimental proof has been lack- 

 ing. He claims to have supplied it by having developed from Aspergillus oryzae an 

 organism having all of the characteristics of true yeasts, i.e., the ability to form 

 ascospores and ferment saccharine materials. His illustrations are quite suggestive. 



Fuchs inoculated Freudenreich flasks filled with sterilized hopped wort with conidia 

 of Aspergillus oryzae. Those flasks which were closed with cotton plugs showed normal 

 growth of the yeast. However, those flasks which were closed with a fermentation valve 

 gave normal growth at first but not after the air had been exhausted. When these flasks were 

 shaken the surface growth fell to the bottom of the liquid. In three weeks the contents of 

 these flasks began to ferment with the appearance of a sediment at the bottom. Microscopic 

 examination, after five weeks, showed the presence of budding ceUs. Fuchs stated that there 

 was little doubt that these budding cells came from the conidia because in some cases the 

 budding cells were stiU attached to the latter. When these cells were transferred to Pasteur 

 flasks and cultivated as yeasts they retained their yeast characteristics. After a longer time 

 (seven months) hat-shaped ascospores characteristic of the genus Willia were seen. While 

 the anaerobic conditions and the presence of sugar were important in this transformation, 

 other factors such as composition of the wort were also important. Fuchs has been unable to 

 transform the yeast cells back to the mold type. He suggested that this would be more 

 difficult. Viala and Pacottet,^ however, reported the development of Gloeosporium ampelo- 

 phagiim from a few yeast cells. 



Some will say immediately that such observations are based upon contaminated 

 cultures. Such an argument, while easy to propose, has been responsible for serious 

 inhibition in the study of the development and forms of microscopic organisms, and 

 should not discourage analysis of Fuch's data. Another attempt to show the close 

 relationship of molds and yeasts was that of Kluyver and Niel,'^ who reported a new 

 genus Sporobolomyces with three species. After these fungi had multiplied by budding 

 in the usual manner, the cells put out organs much like sterigmata at the tip of 



' Fuchs, J.: Cenlralbl. f. Bakleriol., 66, Part II, 490. 1926. 



2 Viala, P., and Pacottet, P.: CompL rend. Acad, scl., 142, 458-61. 1906. 



3 Kluyver, A. J., and Niel, C. B., van: Cenlralbl. f. Bakleriol., 63, Pari II, 1-20. 1924-25. 



498 



