ELECTRON TRANSPORT IN R. RUBRUM 



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 ■ O O AGED CELL 



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Fig. 1. Effect of pH on oxygen consumption by light-grown cells 

 of R. rubriDii. The cells of R. rnbri{))i were grown anaerobically 

 under continuous illumination at 30°C in the medium described by 

 Gest, Kamen, and Bregoff (16). Oxygen uptake was measured by the 

 oxygen-electrode method which had been improved by Hagihara (17). 

 Reactions were carried out at 22° C in darkness and in light (ap- 

 proximately 150 ft-candles) with the cell suspension in the growth 

 medium (approx. 5 mg. dry weight in 2 ml. of reaction mixture). 

 Originally the terms "young" and "aged" cells were adopted to 

 describe cells immediately after incubation for 3 to 5 days and 

 cells allowed to stand for some days in a refrigerator, respectively. 

 At the present time, "aged" cells describes those which had been 

 appropriately aerated in darkness at low temperature (18). 



