Observations on the Formation of the Photosynthetic 



Apparatus in Khodospirillum ruhriim and Some Comments 



on Light-Induced Chromatophore Reactions* 



Douglas C. Pratt, Albert W. Frexkel, and Donald D. HICK^L\^" 



Department of Botany, University of Minnesota, 

 Minneapolis 14, Minn., U.S.A. 



Formation of photochemically active chromatophores in 



the dark 



Cells of R/iodospiri/hini rnhruni when cultured aerobically in the dark 

 were found to be free of chromatophores by Schachman et al. [i]. Vatter 

 and Wolfe [2] and Hickman and Frenkel [3] confirmed this observation. 

 I\Iore recently, Cohen-Bazire et al. [4] demonstrated that when this 

 organism was grown at very low oxygen tensions it was capable of produc- 

 ing chlorophyll. In a more detailed study Cohen-Bazire and Kunisawa [5] 

 studied chlorophyll formation in dark- and light-grown organisms and 

 also measured light-induced phosphorylation carried out by chromato- 

 phores isolated from these organisms. In the study presented here we have 

 concentrated on the efi^ects of oxygen tension on growth, chlorophyll 

 formation, and on structure of dark-grown organisms. We present some 

 preliminary observations [6] which we intend to expand and present in 

 greater detail at a later time. 



EFFECT OF OXYGEN TENSION ON GROWTH AND CHLOROPHYLL 

 FOR\L\TION BY DARK-GROWN CELLS 



In a previous studv [7] it was observed that Rhodospirillum grown either 

 in the dark or in the light had a pronounced CO2 requirement which, 

 except for large additions of either yeast extract or casein hydrolysate, 

 could not be replaced by many common metabolic intermediates which 

 were added either singly or in various combinations to CO2 free culture 

 media. This CO., requirement was found to saturate at about i"„ COg, 

 and all gas mixtures employed subsequently were enriched with either i 

 or 5*^1, COo. In our first experiments dark-grown cultures were gassed 



* Work supported by a grant from the Graduate School of the University of 

 Minnesota, and by grants from the National Institute of Allergy and Infectious 

 Diseases (E-2218), and the National Science Foundation (G-c 



