Synthesis of Nucleic Acids Inescherichia Colv

The utilization of some purines, pyrimidines, nucleosides, and nucleotides for biosynthesis of RNA and DNA bases by E. coli was investigated by the isotopic competition technique. Adenine, adenosine, and desoxyadenosine were found to be precursors of RNA and DNA adenine and guanine. Guanine, guanosine, and desoxyguanosine were precursors of RNA and DNA guanine but contributed only to a limited extent to the synthesis of adenine. Cytosine, cytidine, desoxycytidine, cytidylic acid, uracil, uridine, and uridylic acid were effective as precursors of RNA and DNA cytosine as well as of uracil and thymine. No incorporation of thymine or thymidine was detectable by the method.