THE NUTRITIONAL EQUIVALENCE OF PANTOTHENATE AND p-AMINOBENZOATE FOR THE GROWTH OF BACTERIUM LINENS

Knowledge concerning the function of p-aminobenzoate in biological systems has been derived largely by the use of specific- competitive inhibitors. Thus, the reversal of either sulfa-nilamide or 2-chloro4-aminobenzoate inhibition by methionine and other amino acids (Lampen et al., 1946; King et al., 1948; Strandskov, 1947; Winkler and DeHaan, 1948), by pteroyl-glutamic acid (Nimmo-Smith et al., 1948; Jukes and Stokstad, 1948), and by certain purines and pyrimidines (Cutts and Rainbow, 1949; Lampen and Jones, 1947) has been con-sidered evidence that p-aminobenzoate functions in the synthesis of these metabolites. Similarly, the data of King et al. (1948) imply that p-aminobenzoate also functions in the synthesis of pantothenate since pantothenate effectively antagonized the inhibition of 2-chloro4-amino-benzoate in a mutant of Escherichia coli. High levels of pantothenate also partially satisfied the p-aminobenzoate requirements of a mutant of Saccharomyces cerevisiae (Pomper, 1952). The function of p-aminobenzoate in the synthesis of folic acid or pteroylglutamic acid has been attributed to its incorporation into the pteroylglutamic acid molecule (Angier et al., 1946). Whether p-aminobenzoate is involved indirectly through folic acid or a like metabolite in the synthesis of amino acids, purines, etc., or whether it has a separate catalytic role in the synthesis of metabolites other than pteroyl-glutamate has not been decided conclusively. From a nutritional study of 25 strains of Bacterium linens, it was observed (Purko et al., 1951) that one strain (no. 456) is able to grow when either pantothenate or p-aminobenzoate is present. While an interaction between p-amino-benzoate and pantothenate may be indicated from the use of 2-chloro4-aminobenzoate by 1 A preliminary report was presented at th