title: Escherichia coli deletion mutants illuminate trade-offs between growth rate and flux through a foreign anabolic pathway.
abstract: Metabolic engineers strive to improve the production yields of microbial fermentations, sometimes by mutating the genomes of production strains. Some mutations are detrimental to the health of the organism, so a quantitative and mechanistic understanding of the trade-offs could inform better designs. We employed the bacterial luciferase operon (luxABCDE), which uses ubiquitous energetic cofactors (NADPH, ATP, FMNH2, acetyl-CoA) from the host cell, as a proxy for a novel anabolic pathway. The strains in the Escherichia coli Keio collection, each of which contains a single deletion of a non-essential gene, represent mutational choices that an engineer might make to optimize fermentation yields. The Keio strains and the parental BW25113 strain were transformed with a luxABCDE expression vector. Each transformant was propagated in defined M9 medium at 37 °C for 48 hours; the cell density (optical density at 600 nanometers, OD600) and luminescence were measured every 30 minutes. The trade-offs were visualized by plotting the maximum growth rate and luminescence/OD600 of each transformant across a "production possibility frontier". Our results show that some loss-of-function mutations enhance growth in vitro or light production, but that improvement in one trait generally comes at the expense of the other.
authors: Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, United States of America.
authors: Kelly C
authors: KC
authors: Falls
authors: Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, United States of America.
authors: Aimee L
authors: AL
authors: Williams
authors: Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, United States of America.
authors: Anton V
authors: AV
authors: Bryksin
authors: Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, United States of America.
authors: Ichiro
authors: I
authors: Matsumura
mesh_terms: D002452:Cell Count; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development*; D029968:Escherichia coli Proteins / Q000235:genetics; D005285:Fermentation / Q000235:genetics / Q000502:physiology; D008027:Light; D049453:Luciferases, Bacterial / Q000235:genetics / Q000378:metabolism; D049449:Luminescence; D008660:Metabolism / Q000235:genetics* / Q000502:physiology*; D009876:Operon / Q000235:genetics; D017384:Sequence Deletion / Q000235:genetics*
chemical_list: D029968:Escherichia coli Proteins; D049453:Luciferases, Bacterial