THE LIPOIDS OF MICRO-ORGANISMS 371 



where x and y are 9 to 12 and z is equal to or 1. The 

 most probable structure is ethyl-n-decyl-zz-dodecjd acetic 

 acid. 



The fats of the acid-fast bacilli are peculiar in that the 

 fatty acids are linked to the disaccharide trehalose, in 

 the case of the human tubercle bacilkis and M. leprce, 

 and to an unidentified substance in the case of bovine 

 and avian tubercle bacilli and not to glycerol. 



The fat of the diphtheria bacillus consists mainly of 

 free fatty acids, of which the solid saturated fatty acid, 

 constituting about one -third, is exclusively palmitic acid ; 

 the chief liquid unsaturated fatt}^ acid is A^-hexadecenoic 

 acid, CH3(CH2)5CH=CH(CH2),COOH ; 1 per cent, of the 

 fatty acids consists of an unsaturated acid, C14H26O2 ; 

 a higher unsaturated fatty acid, diphtheric acid, CgsHggOs, 

 m.p. 35°, was also isolated. 



Lactobacillus acidophilus yields lauric, myristic, pal- 

 mitic, stearic and oleic acids, together with a dihydroxy- 

 stearic acid having an optical rotation [a]D + 7-8°. 



In yeasts butyric, caproic, lauric, palmitic, stearic, 

 oleic, linoleic, linolenic, arachidic, myristic and isocetinic 

 acids have been found. The yeasts normally contain about 

 18 per cent, of fat, but End. vernalis and Oospora [Oidium] 

 lactis can produce up to 50 per cent., whilst Toriila 

 lipofera has been shown to give as much as 60 per cent, 

 of its dry weight as fat. The yeast fats usually contain a 

 high proportion of unsaturated fatty acids, oleic and 

 linoleic acids, and are accordingly usually liquid, closely 

 resembling olive oil. 



The mould fats contain palmitic, stearic, tetracosoic, 

 C24H48O2, oleic, linoleic and linolenic acids, in the pro- 

 portion of approximately one-third saturated acids and 

 two -thirds unsaturated acids. 



Waxes, Sterols and Higher Alcohols. — The waxes are 

 esters of fatty acids with higher monohydric alcohols 

 instead of with glycerol as in the fats. The sterols are 

 unsaturated alcohols having a condensed ring structure 



