CHEMISTRY OF CELL WALLS 49 



a number of Gram-negative bacteria are given in Table 20. 

 One of the most important recent developments in the 

 study of the chemistry of the walls of Gram-negative bac- 

 teria has been the recognition of mucopeptide constituents 

 of a similar nature to those forming the whole cell-wall 

 structure of Gram-positive bacteria. This discovery has fol- 

 lowed from a nvuiiber of investigations on the occurrence 

 of DAP 20 and the detection of both DAP and muramic acid 

 in the walls of Escherichia coli -i-'^- and those of a variety of 

 Gram-negative bacteria. ^2- ^- Furthermore, Park ** reported 

 the presence of D-glutamic acid in Escherichia coli walls, 

 and a small amount of D-alanine was detected in the wall of 

 Rho do spirillum rubriim^- Additional evidence for the ex- 

 istence of the mucopeptide in Escherichia coli wall came 

 from the work of Weidel and Primosigh ^^.'s when they dis- 

 covered that the phenol-insoluble fraction of the wall con- 



TABLE 20 



Lipid and Amino Sugar Contents of the Walls of Gram-Negative 



Bacteria 



% Dry Weight Cell Wall 



References 13, 14, 22. 



