COMPOSITION OF BACTERIAL CHROMATOPHORES 



J. W. NEWTON 



Pioneering Laboratory for Microbiological Chemistry, 



Northern Utilization Research and Development Division, 



Agricultural Research Service, U. S. Department of Agriculture, 



Peoria, III. 



An understanding of the function of chromatophore material must 

 ultimately depend upon knowledge of what is present in association 

 with the pigment complex. In addition there is the feature, unique 

 perhaps to photosynthesis as a problem, of the primary process being 

 separated in time from subsequent biochemical events by a large 

 order of magnitude. Hence, as frequently pointed out by Franck, a need 

 arises for appreciable concentrations of biochemically useful reagents 

 to be present in the chromatophore if these reagents are to be coupled 

 effectively to the photochemical process. Possibly the photosynthetic 

 cell has solved this problem in a way that is still obscure, but for the 

 moment one assumes that coupling of the photophysical and photobio- 

 chemical events is reasonably direct and that a knowledge of the con- 

 centration of the various chromatophore components is very relevant 

 to the problem. 



Gross Composition. 



The variable cultural conditions under which photosynthetic bacteria 

 can be grown (1) and the changes which take place within these cells 

 make it extremely difficult to identify essential chromatophore com- 

 ponents by anything other than functional criteria. If one limits chro- 

 matophore function to the primary photochemical act, then by definition 

 the only unambiguous component is bacteriochlorophyll. The problem 

 thus becomes one of finding components always associated with the 

 pigment complex in order to obtain clues to fvinctional relationships. 

 Further complicating this situation is the fact that the internal struc- 

 ture of the cells of photosynthetic bacteria varies under different 

 growth conditions (2); hence attempts at isolating the photosynthetic 

 apparatus in anything resembling its "native" state are at the moment 

 complicated, although some progress has been made along these lines 

 (3). 



Bearing in mind the potential compositional variation in chromato- 

 phore material, one can take as a first approximation to gross chro- 

 matophore composition some early data on C/zrowa^mw chromatophore 

 fractions illustrated in Table 1 (4). Such data led to the recognition 



469 



