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. Author manuscript; available in PMC: 2012 Aug 1.
Published in final edited form as: Curr Opin Biotechnol. 2011 Aug 1;22(4):595–600. doi: 10.1016/j.copbio.2011.03.006

Figure 1. Cellular objectives and selective pressures guiding pathway evolution.

Figure 1

Theoretical (a,b) and experimental (c,d) approaches have been used to gain insight into how the interactions between cellular objectives and selective pressures guide the evolution of metabolic pathways. Specifically, these efforts have shown how (a) microbes gain and lose pathways with an objective to gain biomass under the pressure of limited nutritional resources, and that (c) the metabolic pathways used are consistent with the in silico-predicted optimal pathways. In addition, cells also have an indirect objective of self-protection against a selective pressure of stressful environmental conditions. Consistent with this, (b) adaptation to different temperatures correlates with topological changes in metabolic pathways, and (d) microbes evolve mechanisms to metabolize or protect against toxic environmental conditions.