title: Impact of plasmid size on cellular oxygen demand in Escherichia coli.
abstract: Escherichia coli DH5alpha harbouring either pBGS18, a 4.4 kb pUC-based plasmid, or pQR150, a 20 kb derivative of pBGS18, were grown in glucose-limited chemostat culture to investigate the effects of plasmid size and recombinant protein production on oxygen demand. Under non-induced conditions, where no recombinant protein was expressed, the cellular oxygen demand of cells harbouring pBGS18 and pQR150 was not significantly different, mean specific oxygen uptake rate (OUR) being 0.75+/-0.24 and 0.78+/-0.32 mmol/h per mg of plasmid respectively. Under isopropyl beta-D-thiogalactoside-induced conditions, where recombinant protein was expressed, cells harbouring pBGS18 demonstrated a statistically insignificant 37% increase in mean specific OUR while those harbouring pQR150 demonstrated a statistically significant 415% increase. It is concluded that plasmid size does not significantly affect oxygen demand and that increasing oxygen demand observed with increasing plasmid size is due to production of recombinant protein.
authors.affiliation: The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, Torrington Place, London WC1E 7JE, UK.
authors.forename: Alison
authors.initials: A
authors.lastname: Kay
authors.forename: Ronan
authors.initials: R
authors.lastname: O'Kennedy
authors.forename: John
authors.initials: J
authors.lastname: Ward
authors.forename: Eli
authors.initials: E
authors.lastname: Keshavarz-Moore
mesh_terms: D003470:Culture Media; D004279:DNA, Viral / Q000032:analysis; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000737:chemistry; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism; D009930:Organic Chemicals; D010100:Oxygen / Q000378:metabolism*; D010957:Plasmids / Q000648:ultrastructure*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics
chemical_list: D003470:Culture Media; D004279:DNA, Viral; D005456:Fluorescent Dyes; D009930:Organic Chemicals; C099476:PicoGreen; D011994:Recombinant Proteins; D005947:Glucose; D010100:Oxygen