86 THE BACTERIAL PHOTOCHEMICAL APPARATUS 



SUMMARY 



Thin sections of the green photosynthetic bacterium Chlorobium 

 thiosulfatophilum strain L are unlike other photosynthetic organisms 

 in that no lamellar or chromatophore-like structures appear in the 

 cell. A homogeneous fraction containing the photosynthetic pigments 

 can be isolated and shows the capacity to catalyze photosynthetic 

 phosphorylation. This particulate fraction is by far the simplest photo- 

 chemical system thus far described. The intracellular origin of this 

 fraction, particularly in relation to the bacterial cytoplasmic mem- 

 brane, is not clearly understood at this time. 



In the purple sulfur bacterium Chromatium strain D, where the 

 classical chromatophore structure has always been observed in sec- 

 tions of cells, a complex intracytoplasmic membrane system is pro- 

 duced under certain environmental conditions. The pigment and lipid 

 contents of the cell increase sharply when low light intensities are 

 used for growth. The structure of the photochemical apparatus and the 

 physical and chemical environmentof the bacteriochlorophy 11— reflect- 

 ed by the fine structure of its far red spectrum— are under control of 

 both incident light intensity and metabolic conditions of growth, 



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