Guanosine polyphosphate production of Escherichia coli stringent and relaxed strains in the stationary phase of growth.

Abstract

Stringent and relaxed Escherichia coli strains grown on minimal and on differently enriched media produced guanosine polyphosphates in the stationary phase of growth. On transition from the logarithmic to the stationary phase, stringent strains started to produce guanosine 5' triphosphate 3' diphosphate (pppGpp). and guanosine 5' diphosphate 3' diphosphate (ppGpp), while relaxes strains accumulated only ppGpp. When the stringent strain was cultivated on media enriched with Casamino Acids the leve of pppGpp decreased, while with yeast extract an almost twofold increase could be observed. The concentration of ppGpp increased with both nutrients as compared to that measured in minimal medium. Readdition of glucose to the stationary phase culture did not result in the slightest decrease of the nucleoside polyphosphate levels. In contrast, addition of a mixture of 20 L-amino acids or Casamino Acids or yeast extract to the medium caused an abrupt decrease in the guanosine polyphosphate levels. Qualitatively similar results were obtained with the relaxed strains except that the amounts of ppGpp were smaller than in the case of the stringent counterpart and the responses to the resupplementation were slower. Some possible mechanisms regarding the occurrence of guanosine polyphosphates in the stationary phase are discussed.