48 FATTY ACID METABOLISM IN MICROORGANISMS 



Cri.3 CH3 



I I 



H3C— (CH2)x— CO OC— (CHs)^;— COOH 



(I) (ID 



The gas-liquid chromatographic identification of the 

 methyl ketones resulting from the chromic trioxide oxida- 

 tion of the products of hydrogenolysis (Fig. 1.3; structure 

 III) provides another means for locating the position of 

 the methylene bridge in cyclopropane fatty acids. Thus, 

 the formation of a mixture of 2-nonanone and 2-octanone on 

 oxidation of the hydrogenolysis products derived from a 

 methylenehexadecanoic acid from an E. coli species locates 

 the methylene bridge between positions 9 and 10 (6). These 

 experimental results corroborate fully the assumption, 

 stated in Chapter 1, section 2, that the hydrogenolysis of 

 cyclopropane fatty acids brings about formation of an in- 

 separable mixture of methyl branched fatty acids plus that 

 straight chain fatty acid containing the same number of car- 

 bon atoms as the original compound. 



5. CYCLOPROPANE RING BIOSYNTHESIS 



Studies on fatty acid interconversions in lactic acid or- 

 ganisms which were presented in Chapter 2, section 3, sug- 

 gested a close metabolic relation between aVvaccenic acid 

 on the one hand and lactobacillic acid on the other. • 



Experiments to be discussed in this section demonstrate 

 that the biosynthesis of lactobacillic acid in L. arahinosus 

 proceeds in the manner illustrated in Fig. 2.6. A one- 

 carbon fragment, through as yet unelucidated mechanisms, 

 is added across the double bond of aVvaccenic acid which 

 provides the source for the entire carbon chain of the 



