Regulation of membrane phospholipid synthesis by the relA gene: dependence on ppGpp levels.

A series of experiments using a pair of isogenic rel+ strains of Escherichia coli differing only in the spoT locus has demonstrated a quantitative correlation between the inhibition of phospholipid synthesis and the intracellular level of ppGpp. The conditions examined were (1) amino acid starvation; (2) release from amino acid starvation; and (3) balanced growth. We also have been shown the presence of a third gene (in addition of relA and spoT) concerned with ppGpp metabolism and have been found that the level of ppGpp during amino acid starvation is unaffected by an increase in the dosage of the relA gene.