230 



Paulette Chaix 



fraction III has no mitochondria and contains only free granules of homo- 

 genous size (Vanderwinkel, De Denken and Wiame, 1958). 



The low-temperature spectrum of fraction I (mitochondria), after reduc- 

 tion with succinate, is exactly the same as that of the whole cell in the exponen- 

 tial phase of aerobic growth (Chaix and Heyman-Blanchet, 1957) (Fig. 4, 

 spectrum 1). If the reduction is carried out by sodium dithionite under the 

 conditions previously described (Chaix, Petit, Monier and Zajdela, 1959) the 

 by. and c^a bands are strengthened (Fig. 4, spectrum 2). The presence of 

 cytochrome c in the spectrum indicates that the polyvinylpyrrolidone medium 

 used for the isolation of the mitochondria conserves their integrity better 

 than the 0-5 m lactose (Fig. 4, spectrum 4 and 5), or the phosphate buffer 

 media that we have used in previous experiments. It is probably because the 

 mitochondria that he had isolated were altered that Chance (1957) found 

 spectra partly lacking cytochrome c. 



The spectrum of fraction II shows the Cja and bcL components, and in 

 certain preparations a weak ca band; fraction III contains only relatively 

 weak qa and by. bands (Fig. 4, spectrum 3). 



These experiments, by confirming the presence in aerobic mitochondria of 

 the {a 4- ^3), b, c^ and c components and by excluding the existence of an 

 extra-mitochondrial cytochrome c raise the question whether two other 

 components, reducible by dithionite only and of which the alpha bands 

 would occupy the same positions, are not superposed on b and q. 



(d) Morphological and Spectrographic Properties of Fractions Isolated from 

 Anaerobic Yeast 

 Examination by the electron microscope reveals that fraction I is composed 

 of denser and smaller mitochondria than the aerobic mitochondria, mixed 



Fig. 5. Spectrum of fraction II of anaerobically grown yeast cells harvested 

 during the exponential phase of growth. NagSjOi-reduced. 



