[Stringent control of relA gene transcription in cells of Escherichia coli].

Regulation of E. coli K12 relA gene transcription was studied. The rate of relA-RNA synthesis was measured by RNA-DNA-hybridization technique using cloned fragment of relA gene. Under seryl-tRNA deficiency the rate of relA-RNA synthesis was reduced six times in the strain CP78 (relA+) and only two times in its' relA-variant CP79. Chloramphenicol addition stimulated the rate of relA-RNA synthesis in starved relA+ cells. It was concluded that relA gene transcription is under "stringent control". The rate of relA-RNA synthesis increases proportionally with bacteria growth rate. Grown in glucose-minimal media strain with several copies of relA gene exhibits elevated ppGpp level (50 pmol/A450) and reduced rate of relA-RNA synthesis per one copy of relA gene. Thus, relA gene transcription is under negative regulation of ppGpp.