STRUCTURE OF PHOTOSYNTHETIC SULFUR BACTERIA 



79 



Fig. 5. Electron micrograph of thin section of Chromntiiou strain D grown at 

 low light intensity (see text). 



small chromatophores as appear in Chromatium have limited us in 

 further speculation concerning a structural association. 



Variations in the far- red region of the absorption spectrum of 

 bacteriochlorophyll have also been a subject of considerable specula- 

 tion. The wide diversity of the in vivo spectrum of this pigment in a 

 variety of photosynthetic bacteria is shown in Fig, 6. The divergence 

 in spectra of Chromatium is caused by different nutritional conditions 

 of growth (see below). Wassink et al . (17) have reported variations in 

 the far-red chlorophyll spectrum of Chromatium, anditwas suggested 

 that the multiplicity of absorption maxima represented varieties of 

 bacteriochlorophyll-protein complexes produced under different condi- 

 tions of growth. Cohen-Bazire, et al. (18) and Bergeron and Fuller 

 (19) demonstrated changes in the in vivo spectrum of bacteriochloro- 

 phyll that were associated with carotenoid deficiency. Wassink and 

 Kronenberg (20), however, were able to grow carotenoid deficient cells 

 of Chromatium with a relatively normal spectrum. Bril (21) has re- 

 cently confirmed Wassink' s observations and points out that these 

 divergent experimental results are not readily explained. One point 

 is clear, viz., that alteration of the fine structure in the far-red spec- 

 trum is not due directly to carotenoid deficiency. Frenkel and Hick- 



