28 



THE BACTERIAL PHOTOCHEMICAL APPARATUS 



that of OH-spheroidenone, The same is true for the decrease and in- 

 crease in the concentration of spirilloxanthin and P518, and also for 

 the concentration changes of spheroidene and spheroidenone. The re- 

 sult can best be interpreted in terms of three pairs of transformations, 

 a), b) and c) indicated by the horizontal arrows in Fig. 2, although 

 the reactions mentioned above (vertical arrows) evidently took place 

 also during this experiment, but to a lesser extent. 



The path which we suggest (29) for carotenoid synthesis in /?/?s. 

 gelatinosa, can therefore be structurally depicted as shown in Fig, 4, 



The scheme is based on the results of the kinetic studies cited 

 above and the presence of minor carotenoids in large scale anaerobic 

 cultures, e.g., chloroxanthin (XII), anhydrorhodovibrin (VIII), rhodo- 

 vibrin (IX) and monodemethylated spirilloxanthin (X) (8). Anew carot- 

 enoid with physical properties strongly indicative of a 2-keto- 

 rhodovibrin (XVIIb) has recently been isolated in minute amounts (30), 

 Demethylated spheroidene (XIH) and OH-P518 (XX) are hypothetical 

 intermediates, and have not yet been isolated. 



Since the qualitative distribution pattern of carotenoids in Rps. 

 spheroides (5,9,10,11) and Rps. capsulata (5) is rather similar to that 

 in Rps. gelatinosa (4,8), it can be tentatively assumed that the carot- 



C©o 



H,CO 



Arfiydro-rhodo 

 vibrin (M) 3\ 



H,CO 



H,CO 



OfTirt^yated 

 / I spheradeneODID 



'>^^^,Aw^<y-o-Y^v^v%/^ -S. 



^ I OH- Spheroidene (ZE 

 1 jlW 



3"" 



1 I OH-Sp 

 ' 1(0H-R) 



Spheroidenoned ) 



^J^ «i 2-teto-rhodovibrinanib) 



Fig. 4. Structural scheme for the pathway of carotenoid biosynthesis in liliodo- 

 l)seudomonas gelatinosa (29). 



