6 NUTRITION FACTORS IN YEAST AND BACTERIA 



of this organism was prepared as follows: A fresh beef- 

 heart, devoid of fat, and finely chopped, was boiled for five min- 

 utes with an equal weight of distilled water; the infusion was 

 strained through cloth and filtered, clear, through filter paper. 

 This beef-heart infusion was boiled for 15 minutes with two 

 per cent of its weight of norit charcoal; the decolorized liquid 

 (to be referred to hereafter as D. I.) was filtered clear, and 

 mixed with an equal volume of a glucose-salt solutionf (to be 

 termed G. S.). This mixture was boiled for several minutes, 

 filtered, adjusted to a PH of 7.4 and sterilized in lots of 250 cc. 

 at ten pounds pressure for ten minutes. This medium (referred 

 to hereafter as D.I.-G.S.), inoculated with streptococcus, failed 

 to give growth when used alone, whereas the original undecolor- 

 ized heart infusion was favorable for the growth of this 

 organism. 



EFFECTS OF VARIOUS MEDIA ON GROWTH OF STREPTOCOCCI. 



The tests on streptococci were made as follows: Duplicate 

 tubes were prepared containing nine cc. of the D.I.-G.S. solu- 

 tion plus one cc. of the solution to be tested, one tube being 

 inoculated and the other acting as a sterile control. One set of 

 duplicate tubes of D.I.-G.S. alone, and another set containing this 

 solution plus one per cent peptone, were used as additional sterile 

 and inoculated controls. The inoculations were made from a 

 24-hour bouillon culture previously inoculated from a pure blood 

 culture. 



The original undecolorized heart infusion gave a profuse 

 growth when inoculated with streptococci, while the decolorized 

 medium, either alone or together with the glucose-salt solution, 

 failed to give growth. The decolorized medium, however, gave 

 growth when one percent peptone was added to it, while one 

 percent peptone solution alone or together with glucose-salt solu- 

 tion, failed to give growth. This confirms some of the results 

 obtained by Mueller. 1 



Autolyzed brewers' yeast, diluted 20 times, when added to 

 the D.I.-G.S. medium, supported the growth of streptococci ; but 

 in some cases the growth was retarded, due probably to the 

 strong acid reaction of the autolyzed yeast. When the reaction 



f The glucose-salt (G. S.) solution consisted of an aqueous solution of: NaO 1.0%; 

 CC1 0.02%; MgSO 4 0.04%; KHPO 4 0.20%; Glucose (Difco) 0.20%. 



