34 P-AMINOBENZOIC ACID 



folic acid, pteroic acid, pteroyltrigiutamic acid, or p-aminobenzoylglutamic 

 acid. 



More recent studies by Strehler'"* have shown that methionine satisfies the 

 PABA requirement of a PABA-less mutant of Neurospora crassa^^ produced 

 with nitrogen mustard. Apparently methionine has not been tested for 

 PABA activity with the x-ray induced mutant of Tatum and Beadle,^' ^ 

 the mutant more commonly employed in microbiological assays. If active, 

 it would be a source of interference to be contended with in the conduct 

 or interpretation of assays carried out with Neurosyora crassa. 



2. Synthesis 



The synthesis of PABA by representatives of a great number of bacterial 

 species has been investigated by Landy et al.,^^ using his Acetobader suhoxy- 

 dans assay. '^' '^ Prior to PABA assay, half of each bacterial culture was 

 filtered through a Seitz filter while the other half was adjusted to pH 5.0 

 and hydrolyzed by autoclaving at 120° for one-half hour. The PABA 

 values for cells were calculated from the difference in assay between that 

 found for the whole culture and that found for the medium. A summary of 

 the data obtained is contained in Table VII. Note that in most instances the 

 bulk of the PABA produced is found in the culture medium rather than 

 in the cells. The method used by Landy et al}^ in preparing samples for 

 assay is not sufficient to break down folic acid or related compounds, so 

 that it would appear that the data obtained are reasonably valid. 



PABA synthesis by Torula uiilis is adversely affected by a deficiency of 

 iron according to Lewis. ^^ Normal yeast cells contain about 60 y of PABA 

 per gram, whereas yeast suffering from iron deficiency contains about 3 y 

 per gram. Lewis et al.~^ showed that immediate separation of yeast cells 

 from medium is essential for retention of PABA activity within the cells. 

 In one experiment 18.3 y per gram was found on immediate separation, and 

 12.0 7 per gram after separation was delayed for 18 hours while the fermen- 

 tation mixture was held at 2°. 



Eppwright and Williams^^ found that the addition of thiamine, pyri- 

 doxine, alanine, and inositol to a synthetic medium is accompanied by a 



» B. L. Strehler, J. Bucteriol. 59, 105 (1950). 



15 W. D. McElroy, J. E. Cushins, and H. Miller, ./. Cellnlnr Camp. Physiol. 30, 331 

 (1947). 



16 M. Landy, N. W. Larkum, and E. J. Oswald, Proc. Soc. Expfl. Biol. Med. 52, 338 

 (1943). 



17 M. Landy and 1). M. Dickon, ./. Biol. L'hcm. 146, 109 (1942). 



18 M. Landy and F. Strcightoff, Proc. Soc. Exptl. Biol. Med. 52, 127 (1943). 

 13 J. C. Lewis, Arch. Biochem. 4, 217 (1944). 



2» J. C. Lewis, J. J. Stubbs, and W. M. Noble, Arch. Biochem. 4, 389 (1944). 

 21 M. A. Eppright and R. J. Williams, J. Gen. Physiol. 30, 61 (1946). 



