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Core Genes Evolve Rapidly in the Long-Term Evolution Experiment with Escherichia coli
Rohan Maddamsetti1,2,3, Philip J Hatcher4, Anna G Green3
1Ecology, Evolutionary Biology, and Behavior Program, Michigan State University, East Lansing, MI.
Genome Biology and Evolution
|April 6, 2017
Summary
Bacteria rapidly evolve core genes under selection in laboratory evolution experiments. However, these rapidly evolving genes are surprisingly conserved in natural Escherichia coli populations, suggesting distinct evolutionary pressures.
Area of Science:
- Evolutionary biology
- Microbial genetics
Background:
- Bacteria exhibit rapid evolution and gene diversification under selection.
- The long-term evolution experiment (LTEE) with Escherichia coli provides a model for studying bacterial adaptation.
- Understanding the relationship between laboratory-evolved genes and natural diversification is crucial.
Purpose of the Study:
- To investigate whether genes rapidly evolving in the LTEE of Escherichia coli also show extensive diversification in natural populations.
- To compare the evolutionary trajectories of core and flexible genes under selection.
- To determine if adaptive mutations in the LTEE modify or abolish protein functions.
Main Methods:
- Identification of approximately 2000 core genes shared among 60 E. coli strains.
- Analysis of nonsynonymous mutations in core and flexible genes during the LTEE.
- Comparison of the conservation of LTEE-selected core genes in natural E. coli strains.
Main Results:
- Core genes accumulated significantly more nonsynonymous mutations than flexible genes during the LTEE.
- Core genes under positive selection in the LTEE were found to be more conserved in nature than average core genes.
- Adaptive mutations in some cases modified protein functions rather than causing loss-of-function.
Conclusions:
- Rapidly evolving core genes in the LTEE are not necessarily the most diversified in nature.
- The constant and simple LTEE environment may drive different evolutionary outcomes compared to natural environments.
- Evolutionary pressures in laboratory settings may lead to fine-tuning or loss of functions not favored in the wild.
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