362 BACTERIOLOGICAL CHEMISTRY 



number of organisms, including Escli. coli, Eherth, typhosa, 

 Sal. paratyphi, Sal. schottmillleri, Shigella dysenterice, 

 Proteus, Serratia marcescens, Ps. ceruginosa, B. ayithracis, 

 Phytomonas tumefaciens and V. comma, with similar 

 results. 



The polysaccharide antigens isolated by these methods 

 are the somatic -antigens of the smooth organisms. 



The polysaccharides of a number of bacteria have 

 been investigated. Shigella dysenterice in the smooth 

 form produces a polysaccharide with a specific rotation 

 [a]D+98°, containing 1-6 per cent, of nitrogen. It has 

 a molecular weight about 5,100 and acid equivalent 

 about 9,000. It contains no protein, no pentoses and no 

 uronic acids. The nitrogen is present as an amino group, 

 which, however, is masked by acetylation (the acetyl 

 content is 5 per cent.). The composition and molecular 

 weight correspond to four hexose units, probably glucose, 

 and one acetamido -hexose unit, all repeated six times. 

 This polysaccharide also appears to be responsible for the 

 heterogenetic reaction between Shigella dysenterice antisera 

 and sheep red blood cells. The polysaccharide-protein- 

 phospholipin complex can be dissociated by treatment 

 with formamide into the non-antigenic phospho-lipin and 

 a polysaccharide-protein moiety which has the properties 

 of the somatic antigen of the smooth organisms. Treat- 

 ment of the complex with trypsin removes the protein 

 and leaves the feebly antigenic phospholipin-polysac- 

 charide. The free polysaccharide is a non-antigenic 

 hapten which gives precipitin reactions with antisera. 

 The polysaccharide-protein complex can be split by 

 solution in 90 per cent, phenol and dialysis to give the 

 polysaccharide hapten and the antigenic protein, which, 

 however, has lost the somatic specificity of the complex. 

 The complex can also be degraded by boiling with 1 per 

 cent, acetic acid, yielding an almost non-antigenic 

 protein whi(;li can he further dissociated by solution in 

 phenol, when a prosthetic group is probably removed. 



