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J. Bacteriol. doi:10.1128/JB.01414-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Divergence and redundancy of transport and metabolic rate-yield strategies in a single Escherichia coli population

School of Molecular and Microbial Biosciences, The University of Sydney, NSW 2006 Australia

^* To whom correspondence should be addressed. Email: tferenci{at}mail.usyd.edu.au.

	Abstract

The energetic efficiency of nutrient uptake and conversion into biomass is a key factor in the ecological behaviour of microorganisms. The constraints shaping the metabolic rate/yield trade-off in bacteria are not well-understood. To test whether metabolic rate-yield settings and physiological strategies evolve towards a particular optimum in a constant environment, we studied multiple Escherichia coli isolates evolving in a glucose-limited chemostat population. A major divergence in transport and metabolic strategies was observed and isolates included inefficient rate strategists (polluters or cheaters), yield strategists (conservationists), as well as various hybrid rate/yield strategists and alternative ecotypes (dropouts). Sugar transport assays, strain comparisons based on metabolomics and Biolog profiling revealed variance to the point of individuality within an evolving population. Only 68 of 177 assayed metabolites were unaffected amongst ten clonally-related strains. The parallel enrichment of rate- and yield-strategists and the divergence in metabolic phylogenies indicate that bacteria do not converge on a particular rate/yield balance or unique evolutionary solutions. Redundancies in transport and metabolic pathways are proposed to have laid the framework for the multiplicity of bacterial adaptations.