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

Abstract

Plasmid pBR322 is amplified following amino-acid limitation in Escherichia coli rel A hosts. In rel A* hosts there was no significant amplification or a much smaller one. Plasmid amplification is due to the relA mutation; when the relA + allele is transferred into the relA mutant 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.

DNA degradation at elevated temperatures after plasmid amplification in amino acid-starved Escherichia coli cells

“…However, they could not increase significantly the production of figlucanase. Riethdorf et al (1989) and Wegrzyn (1995) repoited the lowest amplification efficiency at elevated temperatures for pBR322 and L plasmids, respectively. Here we demonstrate plasmid DNA degradation at elevated temperatures after prolonged amino acid starvation.…”

“…It was demonstrated that the amplification efficiency depends on the kind of replicon, the nature of deprived amino acid, and the cultivation temperature (Riethdorf et al, 1989;Herman et al, 1994a;Wegrzyn, 1995). In both cases (ColEl and h plasmids) the lowest amplification efficiency was observed at elevated temperatures (above 37OC and above 4OoC, respectively).…”

“…Although the mechanisms of plasmid DNA replication during amino acid starvation were investigated (Riethdorf et al, 1989;Herman et al, 1994aHerman et al, , 1994bSzalewska-Pa&z et al, 1994;Herman and Wegrzyn, 1995;Wegrzyn and Wegrzyn, 1995) until now the conditions for DNA amplification in amino acid-starved E. coli cells have been optimized only for two kinds of plasmids, namely ColE 1 (Riethdorf et al, 1989) and h (Wegrzyn, 1995). It was demonstrated that the amplification efficiency depends on the kind of replicon, the nature of deprived amino acid, and the cultivation temperature (Riethdorf et al, 1989;Herman et al, 1994a;Wegrzyn, 1995).…”

Effect of increased ppGpp concentration on DNA replication of different replicons in Escherichia coli

“…The starvation for most amino acids resulted in inhibition of plasmid DNA replication in reiA+ but not in relA-strains (HECKER et a]. 1983, 1985, HERMAN et al 1994a, b, HOFMANN et al 1990, RIETHDORF et al 1989, WI~GRZYN et al 1991a. However, in some cases, ColEl plasmids replicated also in amino acid-starved wild type strains (LIN-CHAO andBREMER 1986, HERMAN et al 1994a, b).…”

Replication and amplification of λ plasmids in Escherichia coli during amino acid starvation and limitation

“…Since it was reported previously that replication of different plasmids during stringent and relaxed response may depend on the nature of the deprived amino acid and on temperature [9, 10, 18], we investigated the replication of λ plasmid DNA in relA + and relA − strains of E. coli starved for different amino acids at different temperatures. Bacteria harboring λ plasmids were grown in minimal medium and starved for a certain amino acid.…”