DANIEL 1. ARNON 503 



Soon after the discovery of pholosynthctic phosiihorylation in 

 isolated (hloroj)lasts, Freiikel (19) reported a similar phenomenon in 

 the photosynthetic bacterinm Rhodospirillum rubrum. Althongh 

 Frenkel snggested that the light-induced ATP formation in bacterial 

 preparations was similar to that in chloroplasts, the similarity seemed 

 inicertain at first, because Frenkel's photophosphorylation system, 

 which was a sonic macerate of R. rubrum cells, differed in several 

 respects from its counterpart in isolated chloroplasts (11). Frenkel's 

 preparations became substrate-dependent after washing; the rate of 

 phosphorylation was doubled on adding a-ketoglutarate (49) . But 

 in later experiments he ruled out the dependence on an added chemi- 

 cal substrate (50) and the equivalence of chloroplast and bacterial 

 photophosphorylation could no longer be doubted. 



Frenkel's findings were followed by those of Williams (177), who 

 demonstrated photosynthetic phosphorylation in cell-free prepara- 

 tions of the obligately anaerobic photosynthetic bacteria. Chromatin??! 

 and Chlorobium. It thus became clear that a common anaerobic 

 mechanism for a light-induced phosphorylation, that does not de- 

 pend on an exogenous chemical substrate or on oxygen consumption, 

 is shared by both green plants and photosynthetic bacteria. The 

 energy conversion process proper seemed to be fundamentally in- 

 dependent of oxygen, although it was still possible that details of 

 mechanisms were different in green plants and photosynthetic bacteria. 



The discovery of photosynthetic phosphorylation in chloroplasts 

 by Arnon et al. (11) and in bacterial particles by Frenkel (49) was 

 confirmed and extended in a number of laboratories^. Photosynthetic 

 phosphorylation in isolated chloroplasts was observed by Avron and 

 Jagendorf (21, 22) , Wessels (168) , and Vennesland and her associates 

 (37, 111) ; in algae by Thomas and Haans (146) and Petrack (120) ; 

 and in photosynthetic bacteria by Geller and Gregory (60) , Geller 

 (59), Kamen and Newton (81), and Anderson and Fuller (3). In 

 later experiments Whatley et al. (174, 175) have shown that photo- 

 synthetic phosphorylation by chloroplasts, which had previously been 

 almost entirely limited to observations on chloroplasts isolated from 

 one species, viz., spinach, is also demonstrable with chloroplasts 



^ Other accounts of the ciiscoveiy of CO^ assimilation and photosynthetic phos- 

 phorylation by isolated chloroplasts arc given by Calvin. In 1956 he ascribed (25, 

 p. 31) the discovery of CO, assimilation by isolated chloroplasts to Boychenko and 

 Baranov (31) and in 1959 he ascribed the discovery f)f both CO. assimilation 

 by isolated chloroplasts and photosynthetic phosphorylation to his own laboratory 

 (36, p. 152). 



