Folic acid, vitamin B₁₂ and nucleic acid synthesis in Lactobacillus casei

Abstract

A relationship between folic acid and certain constituents of nucleic acids in micro-organisms has been known for some time. This has been ascertained more directly by the recent demonstration that partial deficiency of folic acid in a medium otherwise favourable for rapid growth of Lactobacillus casei results in impairment of the synthesis of deoxyribonucleic acid but not of ribonucleic acid. According to Stokes, folic acid may function in an enzyme system responsible for the synthesis of thymine, which in turn is used for forming nucleic acids. Presumably, this takes place through its deoxyriboside thymidine with involvement of vitamin B₁₂, the mediation of which in nucleic acid synthesis has also been shown. This and other functional relationships between folic acid and vitamin B₁₂ suggested an investigation of their effects, singly and together, on nucleic acid metabolism.