relA Gene control of bacterial glycogen synthesis

Starvation of Escherichia coli K12 for an amino acid results in the stimulation of bacterial glycogen synthesis in cells containing the relA+ gene, but not in cells carrying the relA- allele. Similarly, a large difference in glycogen content is demonstrable between relA+ and relA- cells in stationary phase. It is concluded that guanosine 5',3' -bis(diphosphate) (ppGPP) or some related relA -dependent metabolite is involved in the regulation of bacterial glycogen synthesis. Detection of significant basal levels of glycogen in a relA- strain of E. coli and in unstarved relA+ C. coli indicates that relA control is not absolutely required for glycogen synthesis but serves as a signal for modulation in response to nutrient availability.