Chapter 33 



On the Physiology of the Photoautotrophie 

 Purple Bacteria from Lake Beloye 



L. K. OSNITSKAYA 



A he photosynthesizing pui"ple sulfur bacteria are capable of util- 

 izing light energy for the assimilation and utilization of carbonic 

 acid owing to the presence of a cellular pigmental complex. 



Under natural conditions these bacteria commonly dwell 

 where there is light, and usually develop at some depths beneath 

 the cover of the green algae. 



The direct dependence of the development of purple sulfur 

 bacteria on the photosynthetic process indicates that the opti- 

 mum conditions for pliotosynthesis are also most favorable for the 

 development of the bacteria. Thus light is one of the basic factors 

 determining the development of purple bacteria. 



French (2, 3) has shown that in purple bacteria (Athior- 

 hodaceae ) it is possible to observe a relationship between photo- 

 synthesis and the energy of incident light, which may be graphi- 

 cally expressed as a sigmoidal curve. 



A similar tendency of light curves was observed in purple 

 sulfur bacteria ( Thiorhodaceae ) by Wassink and his co-workers 

 (12). Later on Morita (7) confirmed the results obtained by 

 French (3) on other representatives of the nonsulfur bacteria. 

 Clayton ( 1 ) investigated the influence of light on phototaxis in 

 purple nonsulfur bacteria. 



Though the above-mentioned investigators have shown the 

 influence of the light intensity upon the assimilation of CO2 by 

 purple bacteria, they have not dealt with a most essential prob- 

 lem, i.e. the need of various species of purple bacteria for light 

 energy. Besides, the above-cited investigations were carried out 

 as short— term experiments with resting cultures, i.e., cell suspen- 

 sions washed off the nutrient medium by centrifugation and 



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