On the Physiology of the Photoautotrophic Purple Bacteria 343 



tained their viability. On being exposed to light, they reproduced 

 intensely. 



The photosynthetic activity of the isolated bacteria, i.e., 

 their capacity to assimilate carbonic acid under photoautotrophic 

 development was estabhshed experimentally. We carried out 

 quantitative estimations of assimilated carbon dioxide, the bac- 

 terial cell carbon content, the oxidized hydrogen sulfide, the 

 amount of SO4 and the number of bacterial cells in the course of 

 the development of the culture. The methods of analysis were 

 given earlier (8). Table 1 shows that the bacteria developed 

 sucessfully in a medium where carbon dioxide acted as the sole 

 source of carbon. The bacterial development ai^d accumulation of 

 biomass in temis of cell carbon, proceeded in accordance with the 

 consumption of carbon dioxide and the oxidation of hydrogen 

 sulfide to sulphuric acid. 



TABLE 1 



The Consumption of Carbon Dioxide in the Course of 

 Photoautotrophic Development of Chromatium vinosum 



Duration of Number of Consumed CO:, Oxidized 



Experiment Bacteria mMolcs H ,S, Cell Carbon 



(Days) (10^/ml) mMoles (mgr/ml) 



Thus, the bacteria we deal with are actually typical photo- 

 autotrophic specimens which, according to the classical defini- 

 tions of microbiology, are incapable of utilizing ready-made or- 

 ganic compounds as nutrients. However, our further investiga- 

 tions have shown that when exposed to light tlie culture is 

 capable of consuming some organic compounds in tlie absence of 

 carbon dioxide. A detailed description of the methods is given in 

 (9,10,11). 



The results of the investigation of the development of Chr. 

 vinosum on media, where the only sources of carbon were acetic 

 acid, propionic acid and a mixture of propionic and acetic 

 acids, are shown in Table 2. 



The development of Chr. vinosum in an acetic medium re- 

 sults in tlie consumption of 8-9 mMoles of acetic acid in the 



