POLYSACCHARIDES OF MICRO -ORC ANISMS 303 



The polysaccharide and the protein can ])e recombined 

 by solution in formamide and precipitation with alcohol. 

 The conjugated protein gives rise to an antigen having 

 the properties of tlie original somatic antigen of Shigella 

 dysenterice, but the simple protein, when coupled with 

 the polysaccharide, gives a non-antigenic complex, 

 suggesting that the prosthetic group is essential for 

 antigenicity. 



A similar somatic antigen complex has been extracted 

 from the 901 strain of Eberthella typhosa by the tri- 

 chloracetic acid, the trypsin and the diethylene glycol 

 extraction methods. It can be dissociated by boiling 

 1 per cent, a.cetic acid to give an ether soluble phospho- 

 lipin, a water soluble polysaccharide and an insoluble 

 protein. The purified polysaccharide, which has 

 [a]546i+1^8°, 1-2 per cent, of organic phosphorus and 

 less than 0-1 per cent, of nitrogen, is non-antigenic and 

 non-toxic to mice but gives a precipitin reaction with 

 typhoid 0-antisera. The purified protein, containing 

 11-5 per cent, of nitrogen, 0-47 per cent, of phosphorus 

 and having [o^]oier'55'^, i-'^ soluble in alkali but not in 

 aoid and a]3pears to be identical with that from Shiga's 

 bacillus. The two proteins can replace one another in 

 combination with the polysaccharide from either organism 

 to give antigens having specificity which is determined 

 by the polysaccharide. A similar protein has also been 

 obtained from Shigella parady sentence (Flexner 88), it 

 contains 10-7 per cent, of nitrogen and 1-1 per cent, of 

 phosphoms and has [a]546i-50°. 



The virulent Vi strains of E. typhosa yield a similar 

 polysaccharide complex which reacts specifically witli 

 antisera to Vi organisms. 



Different polysaccharides corresponding to the rough 

 (avirulent, Type B) and smooth (virulent, Tyj)e A) 

 variants of Staph, aureus are known. They are acid to 

 litmus, give no protein reactions but contain phosphorus 



