68 FATTY ACID METABOLISM IN MICROORGANISMS 



organism. The results of Bloch et al. (4) (Table 3.3) with 

 oleic acid grown L. planariim and M. phlei are in excellent 

 agreement with our own findings. Thus, one must con- 

 clude that these organisms are unable to convert unsaturated 

 into saturated fatty acids. Their inability to effect the 

 opposite reaction, i.e., desaturation of long-chain saturated 

 fatty acids has been discussed. 



It appears that the major metabolic role of monounsatu- 

 rated fatty acids in the bacteria is that of a precursor for 

 the biosynthesis of cyclopropane or methyl branched fatty 

 acids. The first clue in support of this now well-established 

 fact was our observation (10) that L. delbrneckii, grown on 

 biotin low media in presence of lactobacillic acid, fails to 

 synthesize unsaturated fatty acids. These acids are present 

 in high proportions in the lipids of biotin grown cells. We 

 confirmed these observations with L. arahinosus and L. 

 casei (2). The high degree of labeling of the cyclopropane 

 acid fraction in L. planarum and of the 10-methylstearic 

 acid fraction in M. phlei, when the organisms are cultured 

 on oleic acid-l-C^^ (Table 3.3), shows that "methylation" 



TABLE 3.3 



Transformation of 1-C^^ Oleic Acid by Microorganisms 



L. planarum M. phlei 



c.p.m. X 10-3 c.Yi.m. X 10" 



0^4 Oleate added 760 1350 



Total fatty acids 220 338 



Pahnitic acid 1 20 



Stearic acid 2 2 



C^^ Cyclopropane acid 75 



10-Methylstearic acid 200 



Adapted from Bloch et al., Federation Proceedings, 20, 921 (1961). 



