THE LIPOIDS OF MICRO-ORGANISMS 379 



The phosphatides are widely distributed in inicio 

 organisms and are almost certainly present to more or 

 less extent in all of them. The non-acid-fast organisms 

 contain about 0-5 to 2 per cent., whilst the tubercle 

 bacillus contains about 6-5 per cent, of phosphatide. 



The phosphatides of the tubercle bacillus on hydi'olysis 

 yield palmitic and oleic acids and the two liquid saturated 

 acids, tuberculostearic acid, CigHggOg, and phthioic acid, 

 C26H52O2. The leprosy bacillus phosphatide contains an 

 unsaturated Cie fatty acid. The B.C.G. strain yields also 

 a phosphorylated polysaccharide, giving mannose on 

 hydrolysis. The phosphatides of the acid-fast bacteria 

 contain very little nitrogen (see Table 26) and no choline 

 or aminoethanol. The nitrogen ai:)pears to be in the 

 form of ammonia. 



Phthioic acid appears to be responsible for the forma- 

 tion of the tubercles which are a characteristic of tuber- 

 culosis, since injection of the acid or of various fractions 

 containing it gives rise to their production in experi- 

 mental animals. Tuberculostearic acid is irritant but 

 does not cause tubercle formation. 



The lipoids of the acid-fast bacteria contain, besides 

 the phosphatides and waxes, substances akin to the 

 cerebrosides which, on hydrolysis, yield glycerol, fatty 

 acids and a carbohydrate. The carbohydrates have been 

 identified as mannose, glucose and arabinose. The cyclic 

 hexahydric alcohol, inositol, has also been found among 

 the hydrolysis products of this fraction of the acid-fast 

 bacilli. A comparison of the composition of the phospha- 

 tides of some acid-fast bacilli is given in Table 26 : — 



