MICROBIAL CELL WALLS 



(e) The detection o£ ribitolphosphate polymers in walls 

 and the discovery of the teichoic acids. 

 (/) The detection of O-acetyl groups. 

 (g) The presence of ester-linked alanine. 



The identification of the principal constituents of the 

 walls of Gram-positive bacteria has led to the conclusion 

 that the walls belong to the general class of chemical com- 

 pounds known as mucocomplex substances.^^'^^'^^--^-^^'^^ 

 These mucocomplex polymers can be further subdivided, 

 depending on whether peptide components predominate or 

 whether they are predominantly polysaccharide in nature 

 as below: 



mucopeptides— composed of amino acids and amino sugars 

 mucopolysaccharides— sugars and amino sugars 



It is probable that in some cell walls both are covalently 

 joined so that soluble wall compounds derived either chem- 

 ically or enzymically may be essentially either mucopeptide 

 or mucopolysaccharide but containing minor residues of 

 one or the other. In addition to these two classes of sub- 

 stances, we must now add the teichoic acids 2^' ^^ as major 

 wall compounds. The walls of Gram-positive bacteria may 

 therefore be wholly mucopeptide ^3- ^^ or predominantly 

 mucopolysaccharide, with smaller amounts of mucopeptide 

 as in some streptococcal walls,^* or they may contain muco- 

 peptides, mucopolysaccharides, and teichoic acids. 



Amino-Acid Composition. The distribution of major 

 amino acids has been studied in some detail by Cummins 

 and Harris.23.24,31 Amino acid constituents, and in some 

 cases the monosaccharide components of walls, have been of 

 great taxonomic value. 3^-^- The principal combinations of 

 the major amino acids found in walls are presented in 

 Table 10. It will be seen that in none of the walls so far 



