LACTOBACILLIC ACID 27 



bonded dimer in the racemate, an infinite sheet system of 

 hydrogen bonds appears to link the carboxyl groups in the 

 lactobacilhc acid crystal (Fig. 1.13). 



It is well-known that long-chain monocarboxylic acids ex- 

 hibit trimorphism in both the odd and even series. In 

 efforts to obtain crystals suitable for x-ray intensity measure- 

 ments, a variety of solvents and conditions was employed, 

 but in no instance was there any evidence for more than 

 one crystal form of the cyclopropane acids. The acids 

 crystallized from the melt give powder photographs which 

 are of the same structure as those of the single crystals 

 grown from solution. The cyclopropane ring appears to 

 restrict the number of "economical" modes of packing the 

 long chains into the crystal lattice. 



Although synthesis of lactobacillic acid has not been 

 achieved, there can be little doubt regarding the position 

 of the cyclopropane ring and its cis configuration. 



5. OCCURRENCE OF LACTOBACILLIC ACID AND 

 ITS HOMOLOGS IN BACTERIA 



Based on studies with radioactive tracers, OTeary (34) 

 suggested the presence of a C17 cyclopropane fatty acid in 

 the lipids of an Escherichia coli mutant, and Dauchy and 

 Asselineau (35) isolated an acid of this type from this or- 

 ganism. From an unidentified laboratory strain of E. coli, 

 Kaneshiro and Marr (29) isolated a similar or possibly 

 identical acid and provided convincing chemical evidence 

 for the cyclopropane nature and the Ci5-9,10-location of the 

 methylene bridge. Similar findings were reported by Innes 

 Chalk and Kodicek (36). It is of interest to note that in 

 addition to this cyclopropane acid, which accounts for some 



