On the regulation of guanosine tetraphosphate levels in stringent and relaxed strains of Escherichia coli.

[This corrects the article on p. 493 in vol. 32.].

https://mmbr.asm.org/content/mmbr/32/4_Pt_2/493.full.pdf

Antibiotic inhibitors of the bacterial ribosome.

On the turnover of ppGpp in Escherichia coli.

The aim of this work was the establishment of a novel method to determine the metabolic load on host-cell metabolism resulting from recombinant protein production in Escherichia coli. This tool can be used to develop strategies to optimise recombinant fermentation processes through adjustment of recombinant-protein expression to the biosynthetic capacity of the host-cell. The signal molecule of the stringent-response network, guanosine tetraphosphate (ppGpp), and its precursor nucleotides were selected for the estimation of the metabolic load relating to recombinant-protein production. An improved analytical method for the quantification of nucleotides by ion-pair, high-performance liquid chromatography was established. The host-cell response upon overexpression of recombinant protein in fed-batch fermentations was investigated using the production of human superoxide dismutase (rhSOD) as a model system. E. coli strains with different recombinant systems (the T7 and pKK promoter system) exerting different loads on host-cell metabolism were analysed with regard to intracellular nucleotide concentration, rate of product formation and plasmid copy number.

Barry N. Elkins

Papers

The stimulation of ribonucleic acid synthesis by ribosome inhibitors in amino acid-starved Escherichia coli.