Metabolic changes associated with adaptive diversification in Escherichia coli

During a 1,000 generation evolution experiment, two types of morphologically and kinetically distinct bacteria repeatedly diverged from a common ancestor in a fully sympatric seasonal environment containing glucose and acetate. To investigate the metabolic modifications associated with this adaptive diversification, we compare transcription profiles of the two derived types and the common ancestor. Both derived types share a suite of common metabolic changes that may represent adaptation to the environment preceding the diversification event. These include improved translation efficiency, glucose uptake capacity via the mal/lamB genes, up-regulation of various transporters during stationary phase, and likely disruption of the rbs operon. The diversification event is associated with the over-expression of genes involved in the TCA cycle, glyoxylate shunt, acetate consumption and anaerobic respiration in one type and in acetate excretion in the other. These results reveal that competition for both carbon and oxygen have likely played an important role in the adaptation of E. coli during this adaptive diversification event, where one derived type mainly consumes glucose at a fast rate when oxygen is not limiting, and the other derived type consumes glucose and acetate at a slower rate, even when oxygen is limiting.

Key Words: Sympatric speciation, cross feeding polymorphism, frequency dependence, resource specialization

Online ISS 1091-6490
Copyright 2008 by the Genetics Society of America
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