Basal ppGpp level adjustment shown by new spoT mutants affect steady state growth rates and rrnA ribosomal promoter regulation in Escherichia coli

Edoardo Sarubbi, Kenneth E. Rudd, Michael Cashel

Research output: Contribution to journalArticle

99 Scopus citations

Abstract

This work describes an approach towards analyzing the regulatory effects of variation of guanosine 3′,5′-bispyrophosphate (ppGpp) basal levels in Escherichia coli during steady state growth. A series of strains was derived by mutating the spoT gene (which encodes the major cellular ppGppase) so as to obtain systematic increments in ppGpp basal levels. These strains differ genetically at the spoT locus and, in some cases, also at the relA locus because of the severity of spoT mutant alleles. Measurements of ppGpp revealed a ten-fold range of basal levels during growth on minimal medium. The empirical relationship between ppGpp concentration and growth rate is a simple linear inverse correlation. Tandem rrnA ribosomal RNA promoters, present on a multicopy plasmid, are shown to be differentially regulated over this range of basal levels. The upstream P1 promoter activity shows an inverse exponential relation to ppGpp concentration whereas the downstream P2 promoter is only weakly affected. We conclude that there are systematic regulatory consequences associated with small changes in ppGpp basal levels during steady state growth that probably are part of a continuum with more dramatic effects observed during the stringent response to amino acid deprivation.

Original languageEnglish (US)
Pages (from-to)214-222
Number of pages9
JournalMGG Molecular & General Genetics
Volume213
Issue number2-3
DOIs
StatePublished - Aug 1 1988

Keywords

  • 3-Aminotriazole
  • Growth rate control
  • ppGpp
  • spoT

ASJC Scopus subject areas

  • Genetics

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