NUCLEIC ACID PRECURSORS AND PROTEIN SYNTHESIS

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Abstract
Washed cells of auxotrophic mutants of Escherichia coli, suspended in minimal medium with varying amounts of the required nutrilites, were tested for inductive formation of beta-galactosidase. Pyrimidine- and purine-requiring mutants, and a wild-type E. coli B requiring phosphate, also need these compounds for enzyme induction. Uracil is required for induction of glycerol oxidation; uracil, phosphate and adenine are necessary for formation of the "constituitive" system oxidizing glucose. Induced enzyme activities for lactose, lactate or glycerol remain constant or decrease slowly in the absence of purine or pyrimidine. Little or no increase of ribose, deoxyribose or protein occurs in the absence of the required nutrilite. Induction of lactose utilization in the presence of amino acids indicated that purines and pyrimidines are essential for a process other than amino acid synthesis. Preincubation of E. coli B with mustard gas indicated that net desoxyribosenucleic acid synthesis is not necessary for beta-galactosidase induction. Deficiency of Mg inhibits induction and growth after about 30 minutes, but PABA deficiency has no effect on a PABA-less mutant for at least 90 min. , indicating different effects with different growth factors.