190 



MACROMOLECULAR COMPLEXES 



Fig. 6. An electron micrograph of a thin section of the purple sulfur bac- 

 terium, Chromatium. The organism is smooth-contoured and is bounded by a 

 dual membrane which can separate into two distinct structures, the cell wall (W) 

 and the plasma membrane. The cell is filled with the chromatophores (Ch), 

 which are minute vesicles. These appear as annular images with an outer 

 diameter of about 300 A and a cortical thickness of about 70 A. Large vesicles 

 (V), about 1000 A in diameter, are also visible. The irregular areas of low 

 density (N) are considered to be parts of an irregularly shaped nuclear com- 

 partment. The closely packed chromatophores conceal the small particles which 

 are observed in the fractions. X48,000. 



that the cliromatophores hterallv have to be shaken out of the 

 broken cells. The different rates of sedimentation of the pigmented 

 cell fragments and of the individual chromatophores led us earlier 

 to the artificial and erroneous distinction between "laree" and 



