Fig. 4. Electron micrograph (72 000 x ) of thin sections of the non-photo- 

 synthetic bacterium Eschericliia coli. The cell wall (W) is distinct in suitably 

 oriented sections. The "nuclear" region (N) has a low electron density and con- 

 tains very fine (~40 A) filaments. The cytoplasmic region contains minute particles 

 which are well defined. 



