Pfizer Handbook of Microbial Metabolites 344 



There is increasing evidence that the antibiotics mentioned, 

 lysozyme and bacteriophages, all bring about a similar result, 

 the accumulation or liberation of a fundamental cell waU unit 

 such as the one shown. Lysozyme and bacteriophages are able 

 to liberate the unit from pre-formed walls, while the antibiotics 

 merely block wall synthesis. Also, the unit obtained by lyso- 

 zyme or phage action seems to contain glucosamine as well as 

 muramic acid, and sometimes diaminopimelic acid (a lysine 

 precursor) rather than lysine. There is evidence that N-acetyl- 

 D-glucosamine is a direct precursor of muramic acid. 



COOH 



I 



c=o 



I 



CH2 



I 



CH— OH 



I 

 H2N— CH 



! 



HO— CH 



1 

 HC— OH 



I 

 HC— OH 



I 

 CH2OH 



Neuraminic Acid 



Several neuraminopeptides have been isolated from an E. coli 

 mutant culture, and one of these has been purified.-^ It is com- 

 posed of N-acetylneuraminic acid, glucosamine, alanine, lysine 

 and glutamic, acid. '^" 



A model of cell wall structure in gram-positive bacteria has 

 been postulated :^^ 



P P 



/ . . / . 



M — r^G >M— ^-*G >M -^ G 



t * M = Muramic Acid 



G G = N-Acetyl-D-glucosamine 



...T... P = Peptide Moiety 



P P ' *' • = Lysozyme Action 



/ . / : • 



M — r-^G >M — j->G >M 



« 



29 P. J. O'Brien and F. Zilliken, Biochim. et Biophys. Acta 31 543 

 (1959). 



^° E. Kean, Dissertation. (In press) 



31 Friedrich Zilliken, Federation Proc. 18 966-973 (1959). 



