34 



MICROBIAL CELL WALLS 



found an unknown compound in the walls of lactobacilli. 

 This substance w^as found to be a peptide of lysine and as- 

 partic acid (a-aminosuccinoyllysine), which was more re- 

 sistant to acid hydrolysis. The compound in which the 

 aspartic acid is joined to the eNHs group of lysine was also 

 encountered in hydrolysates of the antibiotic bacitracin. *« 

 Appreciable amounts of ammonia have been found on 

 hydrolysis of cell walls by Ikawa and Snell/^ and if this is 

 not due simply to destruction of wall compounds such as 

 the amino sugars it indicates the possibility that some amino 

 acids may be present as amides. Typical results for the 

 amino acid composition of several lactic acid bacteria from 

 the studies of Ikawa and Snell ^^ are presented in Table 13. 



TABLE 13 

 Amino Acid Composition of Walls from Lactic Acid Bacteria * 



(mg per 100 mg cell wall) 



Streptococcus Lactobacillus Lactobacillus 

 faecalis plantarum citrovorum 



* Data from Ikawa and Snell. ^^ 



