82 THE BACTERIAL PHOTOCHEMICAL APPARATUS 



man (22), Bril (21), and Fuller (10) have noted that chromatophore 

 structure in a single species might be dependent on such factors as 

 groAvth conditions and age of cells and that the far- red fine structure 

 of the spectrum of bacteriochlorophyllmay be related to altered struc- 

 tures. These conflicting observations can now be reconciled. 



Fig. 7 illustrates the dramatic changes that occur in the far- red 

 region of the in vivo absorption spectra; these appear to be dependent 

 upon the light intensity to which the cells are exposed during growth. 

 High light intensity seems to enhance the 850 m/i and especially the 

 890 m// absorption maxima. Heterotrophic conditions of growth seem to 

 depress this effect to some extent. Other carbon sources such as 

 acetate or succinate yield the same spectrum as malate. In previous 

 experiments, where diphenylamine was used to suppress carotenoid 

 synthesis, red cellophane was placed between the light source and the 

 culture bottles to depress the light- catalyzed breakdown of diphenyl- 

 amine. Inadvertently this reduced the effective far- red incident light. 

 Although growth did not appear to be affected, the spectrum was altered 

 in a manner similar to that shown for cells grown at low light in- 

 tensities as seen in Fig. 7. 



STRUCTURAL ALTERATIONS 



Chemical analysis of the cells grown at 7000 and 100 foot-candles 

 of incident light was undertaken, and the results are shown in Table 2. 



TABLE 2 



Cheuiical Analysis o/Chromatium Cells Groirii 

 at High and Low Light Intensities 



