to determine the stringent response , a repression of gene activity during amino acid starvation assumed to be mediated by the effector necleotide guanosine tetraphosphate ( ppgpp ) , of metabolically regulated constitutive genes , we measured the transcription of ribosomal protein genes , the constitutive lac operon , and stable rna genes in a variety of growth media and after amino acid starvation in a rela+/rela pair of escherichia coli b/r strains .
C0040649
transcription
C0035668
rna