LIGHT ABSORPTION BY PIGMENTS in vivO 1855 



previously by Katz and Wassink {cf. p. 704). He found, in Chlorobium 

 thiosulfatophilum, two main absorption peaks at 747 and 457 mju; an 

 ultraviolet band at 338 m/x, and shoulders, indicating hidden bands, at 

 423, 515 and 810 m/x (where Katz and Wassink observed a second strong 

 infrared band). One enrichment culture showed a band peak at 732 

 miJL, instead of 747 mju. 



Barer (1955) also measured the absorption spectrum of ChloroUum. 

 As shown by fig. 37C.34, he, too, found the two main bands at 745 and 455 

 van, respectively. No band at 810 m/x was visible. 



350 370 390 410 430 450 470 490 510 530 550 570 590 610 630650 670 690 710 730750 770790 810 



X(nn^) 

 Fig. 37C.34. Absorption spectrum of green bacteria (after Barer 1955). 



The blue-violet (Soret) band of green bacteria is, in both position 

 and shape, very similar to that of chlorophyll a in green cells; but the 

 position of the red band is quite different. Perhaps this indicates that 

 chlorophyll a is present in these bacteria in a special form (Wassink, 1954, 

 pointed out that 745 m^ is the approximate location of the absorption band 

 of chlorophyll a in crystals!); more Hkely, however, "bacterioviridin" is 

 a compound different from chlorophyll a (although belonging to the same 

 type, as suggested by Fischer and Stern, cf. p. 445), and that its absorption 

 band undergoes — in comimon with that of bacteriochlorophyll — a much 

 wider red shift in the transition from solution to the living cell than does 

 the absorption band of chlorophyll in vivo. 



E.xperiments give even less support for the identification of bacterioviridin with 

 bacteriochlorophyll, suggested by Seybold and Hirsch (1954) on the basis of absorption 

 curves showing both a 750 m^i and an 850 van peak in green bacteria. One can only 

 surmise that the cultures used by these investigators, had been contaminated with 

 purple bacteria. Similarly, Seybold and Hirsch's finding of an absorption band at 



