Regulation of ribonucleic acid synthesis by histidine and methionine during recovery of Escherichia coli from magnesium starvation.

During magnesium starvation of Escherichia coli B, most of the ribosomes break down to low-molecular-weight components. When magnesium is restored to the medium, the cells recover. The rate of recovery can be increased greatly by supplementing the growth medium with a mixture of 21 amino acids. This increased rate of recovery is shown to be due to the effect of only two amino acids, histidine and methionine, which initially stimulate accumulation of cellular ribonucleic acid without increasing the rate of protein synthesis. In contrast, histidine and methionine supplementation to logarithmically growing E. coli B is not as effective in stimulating growth as is the complete amino acid mixture. Since cells recovering from magnesium starvation preferentially synthesize ribosomes, it is possible that histidine and methionine play a special role(s) in ribosomal ribonucleic acid synthesis or stability.