On the Cytochromes of Anaerobically Cultured Yeast 



111 



When the culture reaches 120 CU (spectrum 3), the relative strength of the 

 different bands has changed further; the bands located at 552-5 and 558 m/^ 

 have weakened while the three others have strengthened and a new band has 

 appeared at 540 m//. 



When the culture has reached 178 CU (spectrum 4), the change has pro- 

 gressed further; the bands at 552-5 and 558 m/i have practically disappeared 

 and the four other bands have become sharply accentuated. 



INDUCTION BY OXYGEN OF RESPIRATORY CYTOCHROME 

 COMPONENTS IN YEASTS CULTURED ANAEROBICALLY 



In 1950 Ephrussi and Slonimski showed with resting cells from anaerobic 

 cultures that the simple presence of molecular oxygen was able to induce 

 rapidly the synthesis of the classical cytochrome system of aerobic yeast; 

 it was then thought that yeast cultivated anaerobically showed a single type of 

 spectrum only. We have been reinvestigating such induction phenomena, 



4.0 



3.8 

 4.0 



3.8 



c 



■D 



« 4.0 



o. 



O 3,8 



3.8 



3.4 



550 575 



600 



Fig. 2. Induction by oxygen of 

 the air of the respiratory cyto- 

 chrome system in resting cells of 

 yeast from anaerobic culture on 

 yeast extract medium, harvested 

 in the exponential phase; 32 CU; 

 reduction by endogenous sub- 

 strates. 



550 575 600 625 



A. n\/i 



Fig. 3. Induction by oxygen of the 

 air of the respiratory cytochrome 

 system in resting cells of yeast from 

 anaerobic culture on yeast extract 

 medium, harvested in the stationary 

 phase; 240 CU; reduction by en- 

 dogenous substrates. 



