ISOLATION OF BACTERIOPHEOPHYTIN-CONTAINING 

 PARTICLES FROM RHODOSPIRILLUM RUBRUM'^ 



TORU KIHARA and ALBERT W. FRENKEL 



Department of Botany 



University of Minnesota 



Minneapolis 14, Minn. 



The existence of two or three red peaks in the absorption spectra 

 of members of the Athiorhodaceae and Thiorhodaceae has given rise 

 to much speculation as to their identity. A partial fractionation of 

 detergent-treated chromatophores has been achieved by Bril (1); the 

 resulting material, however, was unstable and was not further identi- 

 fied. 



When two-day-old, actively growing cultures ofR. rubrum are ex- 

 tracted with distilled water or with phosphate buffer (pH 7.0) at 5°C, 

 dilute colloidal extracts are obtained whose ratios of extinction at 

 800 m/i to that at 880 mfi are relatively high as compared with the ab- 

 sorption characteristics of whole cells or of isolated chromatophores. 

 By differential centrifugation it is possible to obtain a preparation 

 which, in the red portion of the spectrum, shows only one peak at 

 794 m/j and none at 880 m/y (Fig. 1). This material can be sedimented 

 by centrifuging at 60,000 x g for 1 hour and is free of cytochrome- 5 50. 

 The spectrum of the resuspended B794 fraction (Fig. 1) also shows a 

 pronounced peak at 364 m/i, but little if any carotenoid absorption. 



When this material is extracted with methanol and the pigment 

 transferred to ethyl ether, it becomes apparent that the spectrum of 

 the extract corresponds to that of bacteriopheophytin obtained through 

 the acidification of chromatographically purified bacteriochlorophyll. 

 This spectrum also is in agreement with published spectra (Fig. 2, 3) 

 of bacteriopheophytin (2). It does not appear likely that the B794 ma- 

 terial represents a decomposition product as it can be obtained most 

 abundantly from cultures of rapidly growing cells and is more difficult 

 to obtain in any quantity from older cultures. The origin and possible 

 role of these particles remains to be determined. 



Methanol extracts of intact cells or of isolated chromatophores from 

 R. nibnim, when prepared in the presence of CaCOs and separated 

 chromatographically, also yield a trace of bacteriopheophytin. We do not 



1 A preliminary communication. This investigation has been supported by grants 

 from the National Institutes of Allergy and Infectious Diseases (E-2218) and the 

 U. S. National Science Foundation (G-9888). 



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