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. Author manuscript; available in PMC: 2011 Oct 1.
Published in final edited form as: Curr Opin Biotechnol. 2010 Jul 14;21(5):670–676. doi: 10.1016/j.copbio.2010.05.011

Figure 1. Illustration of a metabolic tradeoff curve.

Figure 1

Each circle represents a genetically independent and biologically meaningful steady-state growth metabolism (elementary flux mode) for E. coli. The position of each circle represents the metabolism’s resource investment (iron per elementary mode, y-axis) and operational efficiency (Cmoles glucose consumed per Cmole biomass produced, x-axis). The tradeoff curve, highlighted in red, represents the optimal relationship between enzymatic iron investment and the biomass production efficiency from glucose. From left to right, the slope of the tradeoff curve decreases, indicating a more severe penalty to operation costs (Cmole glucose per Cmole biomass) as limitations on iron investment increase. The large plot scale permits approximately 10.3 million of the 10.7 million possible biomass-producing pathways to be shown; the insert shows approximately 1 million pathways. Simulation data included maintenance energy requirements for a 60 minute doubling time.