isolation of photochemically active 



chroma tophores from rhodospirillum 



molischianum'^ 



DONALD D. HICKMAN, ALBERT W. FRENKEL 

 and KONSTANTINE COST^ 



Department of Botany 



University of Minnesota 



Minneapolis 14, Minnesota 



A bacteriochlorophy 11- containing particulate fraction capable of 

 carrying out light-induced phosphorylation has been isolated from 

 cells of Rhodospirillum molischianum.^ The cells from which these 

 particles are derived contain lamellar structures in the cytoplasm 

 (Fig. 1) showing the same characteristics as those described by 

 Drews (1) and by Giesbrecht and Drews (2). When such cells are sub- 

 jected to sonic disintegration followed by fractionation in the ultra- 

 centrifuge according to the procedures described earlier fori?, rubrum 

 (3), a fraction is obtained which contains well-defined particles as 

 indicated in Fig. 2 A, The chromatophores oiR. molischianum, when 

 compared with those isolated from R. nibnim (Fig, 2 B), usually are 

 of greater diameter and also reveal more surface detail in phospho- 

 tungstate- treated preparations. Judging from the appearance of sec- 

 tioned cells, the chromatophores oiR. molischianum are disc shaped, 

 while those of R. rubrum appear to be nearly spherical, Giesbrecht 

 and Drews (2) have described chromatophores in R. molischiamim as 

 consisting of stacks of 5-15 lamellae. The chromatophores described 

 here (Fig, 2 A) appear to be subunits of such stacks. 



Rates of light-induced phosphorylation observed with isolated 

 chromatophores from/?, molischiamim (150-200/^molesorthophosphate 

 esterified as ATP per hour per jumole bacteriochlorophy 11) are com- 

 parable to those reported by us for R. rub mm (3), Thus far we have 

 not been able to elicit photoreduction of pyridine nucleotides by these 

 particles. 



1 This study was supported by grants E-2218 and E-3989 from the National 

 Institutes of Health. 



2 We wish to thank Dr.C.B. van Niel for the culture of Rhodospirillum molisch- 

 ianum . 



3 Holder of Graduate Fellowship from the Charles F. Kettering Foundation. 



Ill 



