The assimilation of amino acids by bacteria. 26. The incorporation of adenine into the nucleic acid of disrupted staphylococcal cells.

Gale & Folkes (1953a, b) showed that there is an inorease in the nucleic acid content of washed suspensions of Staphylococcus aureus (Micrococcu4s pyogenes var. aureus) when these are incubated in the presence of glucose, purines, pyrimidines and a mixture of all those amino acids necessary for protein synthesis. Omission of an essential amino acid resulted in cessation of nucleic acid synthesis. In the presence of the amino acid mixture, protein synthesis also occurred; the addition of a growthlimiting concentration of chloramphenicol gave rise to complete inhibition of protein synthesis but stimulated formation of ribonucleic acid (RNA). A number of investigations with amino acidrequiring mutants has since confirmed that nucleic acid synthesis in bacteria will take place only if all the amino acids required for protein synthesis are either present in the medium or can be synthesized by the organism (Borek, Ryan & Rickenbach, 1955; Gros & Gros, 1956; Pardee & Prestidge, 1956). Pardee, Paigen & Prestidge (1957) and Neidhardt & Gros (1957) have confirmed that RNA synthesis will occur in the presence of chloramphenicol but have shown that the RNA formed under these conditions differs from 'normal' RNA in electrophoretic mobility, molecular weight and stability. Previous papers of this series (Gale & Folkes, 1955, 1958) have shown that removal of nucleic acid from disrupted staphylococcal cells markedly reduces the ability of the preparation to incorporate amino acids and that this ability can be restored by the addition to the incubation medium of deoxyribonucleic acid (DNA), RNA or an 'incorporation factor' prepared from digests of nucleic acid. The present communication describes the conditions necessary for the incorporation of labelled purines into the nucleic acid fraction of disrupted cells, and the role of nucleic acids and the incorporation factor in such processes.