36 FATTY ACID METABOLISM IN MICROORGANISMS 



(Table 2.2); consequently, great care must be exercised in 

 the identification of monoethenoid octadecanoic acids of 

 bacterial origin. Characterization of such acids may be 

 achieved by (1) conversion into the respective dihydroxy 

 derivatives, (2) oxidative cleavage of the latter and identifica- 

 tion of the fragments, and (3) preparation of a number of 

 derivatives and comparison with corresponding derivatives 

 of established identity. Since the x-ray diffraction patterns 

 of the dihydroxy derivatives of isomeric octadecenoic acids 

 exhibit characteristic differences (9), this property also is 

 useful in establishing the position of the double bond. 



Gas-liquid chromatography allows identification of the 

 oxidative split products derived from position isomeric 

 monounsaturated fatty acids containing 16 and 18 carbon 

 atoms, respectively, as they occur in bacterial lipids and 

 makes possible the simultaneous identification of the double- 

 bond position in both classes of acids on a micro scale 

 (4, 10). 



By this procedure, it was shown conclusively that in addi- 

 tion to its presence in L. arabinosus, where it was discovered, 

 c?5-vaccenic acid is widely distributed in bacteria. It occurs 

 as the sole monoethenoid octadecanoic acid in L. casei and 

 mixtures of czVvaccenic acid and of oleic acid are present 

 in the lipids of a Streptococcus species, in E. coli (6) (70% 

 cw-vaccenic, 30% oleic acid), in A. tiimejaciens (10) (90% 

 aVvaccenic, 10% oleic acid), in Azotohacter agilis (10) (80% 

 c/^-vaccenic, 20% oleic acid), and in C. hutyricum (63% cis- 

 vaccenic, 37% oleic acid). Palmitoleic acid (<:zV9,10-hexa- 

 decenoic acid) is contained in the lipids of E. coli (6), L. 

 planarum, A. tumefaciens, and A. agilis (10). Isomers of 

 this acid differing in the location of the double bond are 

 present in a Streptococcus species (11) (c/5-ll,12-hexadeca- 

 noic acid) and in C. butyricum. The C^q unsaturated frac- 



