THE RESPIRATORY SYSTEM OF RHODOMICROBIUM 

 VANNIELII 



S, MORITA and S. F. CONTI 



Department of Microbiology , Dartmouth Medical School 



Hanover, New Hampshire 



The phenomenon of oxygen uptake by a variety of photosynthetic 

 bacteria grown anaerobically in the light has been well documented by 

 a variety of investigators (1). In almost all cases studied, this oxygen 

 uptake was inhibited by light, indicating a close relationship between 

 electron transport involved in respiration and photosynthetic processes. 

 It was observed, however, that oxygen uptake by Rhodomicrobium 

 vannielii was stimulated, not inhibited, by light (2). This process was 

 therefore examined in detail, in the hope that the interrelationship, if 

 any, of electron transport occurring during respiration and photo- 

 synthetic processes could be more clearly defined. 



RESULTS 



Oxygen Uptake. 



Oxygen uptake by intact cells of R. vannielii could be detected both 

 in light and darkness. In the presence of endogenous or added substrate 

 (i.e., succinate) the rate of oxygen uptake in the light was significantly 

 greater than that observed in the dark. Photoinhibition of oxygen uptake 

 was not observed, although in some instances, light had only a small 

 effect on the rate of oxygen uptake. The results are summarized in 

 Table 1. 



TABLE 1. 



Respiratory activity of intact cells of R. vannielii 

 Oumoles 02/Jir/mg. protein) 



Endogenous With Succinate 



Light 0.170 0.223 



Dark 0.148 0.175 



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