On the Physiology of the Photoautolrophic Purple Bacteria 347 

 TABLE 5 



The Dynamics of Development of Chr. vinosum at Exposure Intensities 

 FROM 7.35 to 23.3x103 erg/cm^ sec. 



the purple sulfur bacterium Chr. vinosum is capable of photosyn- 

 thesizing within a broad range of light inten.sities. 



Though the development of the culture is also observed at 

 low light intensity (1.4 thousand erg/cm- sec), the insignifi- 

 cant and slow increase of the cell numbers shows that this light 

 intensity is inadequate to ensure the development of these bac- 

 teria at the expense of photosynthesis. 



Taking into consideration the above-mentioned ability of the 

 exposed purple sulfur bacterium Chr. vinosum to utilize, under 

 light exposure, some organic compounds whose assimilation re- 

 quires a smaller quantity of light energy, it is possible to imagine 

 that in natural habitats and under insufficiently favourable light- 

 ing conditions (the shadiness of tlie environment, profuse de- 

 velopment of phytoplankton etc.) Chr. vinosum develops partly 

 at the expense of photoheterotrophic nutrition. The high intensity 

 of light stimulates a more rapid development of the culture and 

 has the most pronounced effect during the early periods of the 

 culture growth, i.e., during the second and third day. At later 

 periods, i.e., on the fifth to tenth day, the effect of light intensity 

 upon the development of the culture is not so distinct. 



It is possible to assume that during the period of intense cell 

 reproduction the photoautotrophic bacteria (which have no 

 possible way for building cell material other than CO.- photoas- 

 similation) have particular need for light energy to realize this 

 process. At later stages of the culture development tlie effect 

 of light intensity is less pronounced owing to the various bio- 

 chemical processes occurring in the medium. Possibly, this atten- 

 uation of the development of the bacterial culture may be ex- 



