RelAmutation and pBR322 plasmid amplification in amino acid-starved cells ofEscherichia coli

Abstract
Summary: Plasmid pBR322 is amplified following amino-acid limitation inEscherichia coli relAhosts. InrelA+hosts there was no significant amplification or a much smaller one. Plasmid amplification is due to therelAmutation; when therelA+allele is transferred into therelAmutant CP79 this strain no longer amplifies plasmid DNA during amino acid starvation. It is concluded that ppGpp is a negative effector of plasmid replication. Amplification is temperature dependent, being maximal at 32 °C and negligible at 37 °C.