CARTENOIDS OF PHOTOSYNTHETIC BACTERIA 23 



Lycopene is the carotenoid most widely distributed— it is found in 

 13 of the 16 species. The composition of the carotenoid mixture from 

 Rhodopseiidomonas gelatinosa is the most complex, consisting of 12 

 coloured components in cells grown under semi-aerobic conditions. 



In turning to a discussion of the bios5aithesis of these pigments I 

 would like to refer to recent reviews (1,20,21), and to take as the 

 starting point the structural scheme in Fig, 1, suggested for carotenoid 

 biosynthesis in purple bacteria two years ago by Stanier's group (22, 

 23,7). This pathway offered a simple and logical picture of the carot- 

 enoid biosynthesis in non-sulphur purple bacteria. The scheme was 

 based on a number of studies, viz., the carotenoid composition of mu- 

 tants of RJiodopseiidomonas spheroides with deranged carotenoid syn- 

 thesis (24), the diphenylamine- effect and carotenoid transformations 



11 



•C, - cnrotcne (IV) 



11 ■ ' '.' 



3. 



:hl,.roxnnthin ("> 



Ip' 



L^a.^cn 



5.!;° 



OH-V (Mil) 



31 



A^h^J^orhoJ..^.^r,n(VIm 



31 



21 



Rhixluvibnn (1\) 



Spir.lloxamhin (XI) 



Fig. 1. Structural scheme for the pathway of carotenoW biosynthesis in purple 

 bacteria (23,7). 



