42 MICROBIAL CELL WALLS 



amino groups of DAP may be unavailable for reaction with 

 FDNB in a high proportion of the residues in some cell 

 walls.^6 



Muramic acid has been detected (usually by paper chro- 

 matography) in all of the bacterial cell walls so far exam- 

 ined.^^'21'22,24,42 whether the structures are identical in 

 all cases and whether all muramic acids are the 3-O-D-lactyl 

 ethers of glucosamine remains to be established. It is of 

 interest to note that Agien and Verdier ^° have isolated 

 6-phosphoryl muramic acid from a protein-bound com- 

 pound in Lactobacillus casei. It will be of great interest 

 to learn whether this compound occurs in the wall as the 

 phosphoryl derivative. 



In addition to muramic acid, glucosamine is also univer- 

 sally present in bacterial cell walls.13,14,19 Galactosamine 

 has been found, together with muramic acid and glucosa- 

 mine, in some bacterial walls, but it seems to be much less 

 widely distributed.i9'23.24,3i ij- {^ probable that all three 

 amino sugars occur in the walls as N-acetyl or as N-acyl com- 

 pounds. The reaction of walls with FDNB has so far shown 

 that none of the amino groups of the amino sugars is free.^^ 



Monosaccfiar/des. Some bacterial walls are composed 

 entirely of amino acids and amino sugars being devoid of 

 other sugar components. ^^-s" However, many bacterial 

 walls yield monosaccharides on hydrolysis, and the investi- 

 gations of Cummins and Harris 23,24,31 j^^ve shown that the 

 sugar components are characteristic of certain taxonomic 

 groups. Glucose occurs commonly in many bacterial walls 

 and, as will be seen later, it may also be a constituent of 

 the teichoic acid moiety of the wall. Rhamnose, first found 

 as a wall monosaccharide in Streptococcus faecalis,^^ is the 

 typical sugar of the streptococcal group. Arabinose, de- 

 tected in the wall and isolated cell-wall oligosaccharide of 



