VIII. EFFECTS OF DEFICIENCY 33 



relationsliips (see section on sulfonamides) that PABA is a precursor of this 

 vitamin. Maj^cr'' obser\'ed that M ijcolxictcrium tuberculoids produces a yel- 

 low compound in the presence of high concentrations of PABA. Mills el al.^ 

 showed that in the presence of high concentrations of PAB.V M ycohaclerhim 

 luberculosis produces increased amounts of vitamins Bio nnd Bn (fohc acid 

 or its conjugates). Possibly these compounds are responsible for the yellow 

 color originall}^ described by IMaj^er. 



Sarett^ demonstrated that Lactobacillus arabinosus synthesizes folic acid 

 in proportion to the PABA content of the basal medium. The bulk of the 

 folic acid synthesized occurs free in the medium, only a small fraction re- 

 maining in the bacterial cells. The synthesis of folic acid from PABA is 

 largely completed at the end of the log growth period (20 hours) and is 

 greater in acid-hydrolyzed casein medium than in enzymatically digested 

 casein or amino acid medium. Addition of L-glutamic acid does not increase 

 folic acid synthesis. 



The e.\tent to which folic acid can satisfy the PABA requirement of bac- 

 teria is a controversial subject. Sarett^ found that folic acid or pteroic acid 

 has some activity in replacing PABA as a growth factor for Lactobacillus 

 arabinosus. Similarly, Lampen and coworkers^- ^ reported that folic acid, 

 pteroyltriglutamic acid, pteroic acid, or p-aminobenzoylglutamic acid is 

 less active on a molecular basis than is PABA as a growth factor for Lacto- 

 bacillus arabinosus. Koft el aZ.^"'* demonstrated the unstable nature of 

 folic acid and related compounds in solution. It would appear from the 

 data of these investigators that the PABA activity of folic acid for Lacto- 

 bacillus arabinosus is due to the presence of PABA in the compound as an 

 impurity or to the unstable nature of folic acid in solution. 



Folic acid was found by Lampen et al.^^ to be inactive as a source of PABA 

 for a PABA-less mutant of Escherichia coli. As might be expected (see 

 section on sulfonamides) the PABA requirement of this mutant may be 

 satisfied by a combination of amino acids, a purine, and thymine. Under 

 these conditions, however, growth is not optimal. 



Zalokar'^ found that the PABA requirement of the PABA-less mutant of 

 Neurospora crassa described by Tatum and Beadle^ cannot be satisfied bj'^ 



Mt. L. Mayer, Science 98, 203 (1943). 



6R. C. Mills, G. M. Briggs, Jr., T. D. Luckey, and C. A. Elvehjem, Proc. Soc. 

 Exptl. Biol. Med. 56, 240 (1944). 



7 H. P. Sarett, J. Biol. Chem. 171, 265 (1947). 



« J. O. Lampen, R. R. Roepke, and M. J. Jones, /. Biol. Chem. 164, 789 (1946). 



9 J. O. Lampen and M. J. Jones, /. Biol. Chem. 170, 133 (1947). 

 >" B. W. Koft, M. G. Sevag, and E. Steers, /. Biol. Chem. 185, 9 (1950). 

 " B. W. Koft and M. G. Sevag, /. Am. Chem. Soc. 71, 3245 (1949). 

 '= J. (). Lampen, M. J. Jones, and R. R. Roepke, ./. Biol. Chem. 180, 423 (1949). 

 " M. Zalokar Proc. Nail. Acad. Sci. U.S. 34, 32 (194S). 



