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Adaptive diversification in genes that regulate resource use in Escherichia coli
Christine C Spencer1, Melanie Bertrand, Michael Travisano
1Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada. spencer@zoology.ubc.ca
Plos Genetics
|January 24, 2007
Summary
A genetic change allows Escherichia coli to adapt to different resources, creating distinct bacterial types. This study reveals how genetic mutations drive ecological diversification and maintain it through natural selection.
Area of Science:
- Evolutionary biology
- Microbial ecology
- Genetics
Background:
- Adaptive diversification is driven by ecological factors, but the genetic basis of resource-use trade-offs is less understood.
- Stable, diversified ecotypes arise from genetic changes influencing resource utilization and selection pressures.
- Understanding the genetic mechanisms underlying ecological differentiation is crucial for evolutionary studies.
Purpose of the Study:
- To investigate how a regulatory genetic change contributes to sympatric diversification in Escherichia coli.
- To elucidate the genetic basis of differential resource use and negative frequency-dependent selection in bacterial ecotypes.
- To link genetic mechanisms to physiological and ecological diversification processes.
Main Methods:
- Studying adaptation of Escherichia coli to sequential use of glucose and acetate.
- Characterizing two distinct ecotypes: "slow-switcher" and "fast-switcher" based on switching lag.
- Identifying genetic mutations, specifically a transposon insertion in a regulator, affecting acetate metabolism gene (aceB) expression.
- Performing allele-swapping experiments to confirm the role of the identified genetic variant.
Main Results:
- Escherichia coli differentiates into "slow-switcher" and "fast-switcher" ecotypes with different growth profiles.
- The "fast-switcher" exhibits a short switching lag due to the failure to down-regulate acetate metabolism (aceB expression) during glucose growth.
- A transposon insertion in a regulatory gene was identified as responsible for the altered aceB expression and ecological differentiation.
- Genetic manipulation confirmed the transposon's role in differentiating ecological types.
Conclusions:
- Regulatory genetic changes can drive sympatric diversification based on differential resource use.
- A specific transposon-induced regulatory mutation underlies the "fast-switcher" phenotype in Escherichia coli.
- This study provides a mechanistic link between genetic variation, physiological adaptation, and ecological diversification.
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