59° PETER MITCHELL 



TABLE IV 



Glucose 6-phosphatase Activity of Normal and Treated Escherichia 

 coli (ML 30) Suspensions and of Growth and Suspension Media 



Normal intact cells 



(/xmole P/g. min. liberated 



in suspension medium only) 



2-91 



suspension medium. As illustrated in Fig. i, these and other confirmatory 

 observations forced us to the conclusion that the glucose-6-phosphatase of 

 intact Escherichia coli is enclosed in a region between the cell wall and the 

 surface of the osmotic barrier component of the plasma membrane which 



Cell wall 

 (molecular sieve) 



I Plasma membrane 



; Periplasm ''(osmotic barrier) 



Medium 



Endoplasm 



Glucose- 6- phosphate 



Fig. I. Diagram of cell wall, periplasm and plasma membrane (osmotic barrier 

 component) in Escherichia coli. The glucose-6-phosphatase, partly adsorbed on a 

 substratum in the cell envelope complex, is confined to the periplasm by the 

 molecular sieve function of the cell wall. 



we might appropriately call the "periplasm". You may ask how one can 

 show that the effective pore size of the cell wall of living Escherichia coli is 

 small enough to prevent the passage of proteins between the periplasm and 

 the external medium. Figure 2{a) shows living Escherichia coli (strain 

 ML 30) in which the protoplasts have been made to retract from the cell 

 wall by the addition of 0-4 M NaCl to a suspension medium of 0-02 M 

 sodium phosphate buffer at pH 7, and Fig. 2(6) shows the same with the 



