On the Longevity of certain Species of Yeast. 

 Hansen's Yeasts. 



357 



Species. 



Time of first appearance of spores 

 observed in a fresh 24 hours' 

 growth at 25° C. 



Saccli. cereyisiae ' Within 24 hours 



Sacch. ellipsoideus I ' Within 24 hours 



Sacch. ellipsoideus II ' Within 36 hours 



Sacch. Pastorianus I Within 36 hours 



Sacch. Pastorianus II Within 24 hours 



Sacch. Pastorianus III Within 36 hours 



Sacch. exiguus Scanty spores after 36 hours. 



Carlsberg No. 2 ' Within 36 hours 



Size of the spores. 



2i-6M 

 2 -4u 



2 -4a 



H-4m 

 2 -4*1 

 2 -34m 



2 -4J^t 



3 -6n 



We may mention that four species of these yeasts showed a well-marked 

 liquefying power towards gelatin, liquefaction occurring in from 2^ to 4 

 weeks after making the streaks and keeping at the ordinary temperature. 

 The liquefying power occurred in the order shown below : — 



1. Sacch. Pastorianus I. 

 3. Sacch. cerevisise. 



2. Sacch. ellipsoideus I. 

 4. Sacch. Carlsberg, No. 2. 



The other species did not liquefy gelatin, but here it was observed that 

 there was a characteristic tendency for growth to extend into the depth of the 

 gelatin culture medium, 



The fact that after thirty-four years these yeasts were still living is, we 

 think, a point of great scientific interest and importance. In what form they 

 retained their vitality, however — whether as resting cells or spores — cannot, 

 unfortunately, be determined. From the work of Hansen we know that one 

 species at least, S. apiculatm, found on the e.xterior of certain fruits, hiber- 

 nates in the soil, and inasmuch as this species, or at all events the yeast with 

 which Hansen worked, does not form endo-spores, it may be that our yeasts 

 have been preserved as resting cells. 



The only observations at all parallel with our own are those of H. Will,* 

 who showed that certain wild yeasts, on a dry asbestos medium, were still 

 living after seventeen years. They apparently had retained the cell form. 



Further experiments with these and other species of yeasts are in progress 

 in these laboratories. 



' Zeitschrift fiir das gesammte Brauwesen,' 1896-1904. 



