Conversion of uracil to thymine by strains of bacillus subtilis.

From replacement studies (1) and inhibition analysis (2) with microorganisms requiring folic acid, it has been inferred that this vitamin is concerned in the biosynthesis of purines and of thymine. More directly, folic acid has been shown to be involved in nucleic acid synthesis in Lactobacillus casei (3,4). According to Buchanan and Schulman (5), the formation of purine derivatives would seem to require a folic acid-activated enzyme. The observed effectiveness of uracil in large doses in pernicious anemia in relapse has been interpreted to mean that it may be a precursor of thymine (6). Interchangeability of certain pyrimidines in the nutrition of microorganisms is known (7-9). The present study relates to the ability of several strains of Bacillus subtilis to convert uracil to thymine and to the probable role of folic acid and vitamin Blz in this transformation.