Escherichia coli Deletion Mutants Illuminate Trade-Offs between Growth Rate and Flux through a Foreign Anabolic Pathway

• Type of Material: Article
• Authors: Kelly C. Falls, The University of Iowa; Aimee L. Williams, University of Georgia; Anton V. Bryksin, Georgia Institute of Technology; Ichiro Matsumura, Emory University
• Language: English
• Date: 2014
• Publisher: Public Library of Science
• Publication Version: Final Published Version
• Copyright Statement: © 2014 Falls et al.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0088159
• Title of Journal or Parent Work: PLoS ONE
• ISSN: 1932-6203
• Volume: 9
• Issue: 2
• Start Page: e88159
• End Page: e88159
• Grant/Funding Information: AB, AW and IM were supported by MCB-0951076 (NSF2); This work was supported by the National Science Foundation. KF and IM were supported by grant number EF-1104988 (NSF3)
• Research Categories: Chemistry, Biochemistry; Health Sciences, General; Engineering, Biomedical

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.