Sparing Eifect on the Folic Acid Requirement of Streptococcus Lactis by 5-amino-2,4-bis(substituted-amino)pyrimidines1

Enzyme induction in Escherichia coli is stimulated by certain 5-amino-2,4-bis(substitutedamino)pyrimidines (Kunkee, 1960a). Other 2,4diaminopyrimidines have been reported to be antagonists of folic acid (Hitchings et al., 1952; Doctor, 1956). Since there are indications that the stimulation of enzyme induction involves nucleic acid metabolism (Kunkee, 1960b) and since folic acid is involved in nucleic acid precursor synthesis (Rogers and Shive, 1948), we wished to determine what effect the 5-amino-2 ,4bis(substituted-amino)pyrimidines might have on folic acid metabolism. E. coli has no growth requirement for folic acid and enzyme induction in E. coli is not affected by folic acid either in the presence or in the absence of the compounds which stimulate induction (Kunkee, 1960a). Therefore, to discover a relationship between folic acid and the substituted pyrimidines, we studied the folic acid requirement for growth of streptococci.