8 NUTRITION FACTORS IN YEAST AND BACTERIA 



Undecolorized beef-heart infusion gives a growth of yeast 

 cells which compares favorably with that produced by a 5% 

 solution of autolyzed yeast itself. The addition of glucose to 

 autolyzed yeast has very little if any additional activating prop- 

 erty, other than that of slightly enriching the medium. One cc. 

 of decolorized heart infusion when added to the Nageli solution 

 with or without the glucose-salt solution, has little or no effect on 

 yeast cells; while the D.I.-G.S. medium containing one percent 

 of peptone, when added to the Nageli solution, stimulates the 

 growth of yeast cells just exactly as much as when one percent 

 peptone solution alone is added. 



TABLE II. 



Effects of various media on the growth of yeast cells. 



Net yeast 



Substance added to 9 cc. of standard Nageli solution Growth in 



No. mm. 



1. 1 cc. 5% autolyzed yeast (5 CQ. in 95 cc. water) 10.0 



2. Ice. 5% autolyzed yeast -f- 1 cc. 10% glucose solution (Difco) 11.0 



3. 1 cc. D. I. solution alone 0. 



4. 1 cc. D.-I.-G. S. solution 1.5 



6. 1 cc. 1% peptone solution (Difco) 2.5 



6. 1 cc. D. I.-G. S. solution containing 1% peptone 4.0 



7. 1 cc. G. S. solution 0. 



8. 1 cc. G. S. solution containing 1% peptone 2.0 



9. 1 cc. Undecolorized meat infusion , 7.5 



10. 1 cc. Undecolorized beef -heart infusion 12.0 



It is apparent from the results shown in tables I and II, 

 that there is present in beef and beef-heart infusions, and in 

 peptone and autolyzed yeast, a substance that shows compar- 

 able growth-stimulation on hemolytic streptococci and yeast cells. 

 The question now naturally arises as to the nature of the sub- 

 stance that shows such a marked similarity of effect on these 

 two organisms. From the standpoint of the favorable action on 

 yeast cells, we are probably dealing here with one or more sub- 

 stances of the class of B vitamine. As for the growth-influencing 

 action on streptococci, this either is due to a substance of an 

 identical or similar nature; or, as suggested in the work of 

 Davis, 3 Rivers and Poole, 4 and others, we are dealing with two 

 unknown substances, one or both of which may belong to the class 

 of vitamines. These authors found that certain organisms, par- 

 ticularly those of the hemophilic type, require two substances^for 



