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A ratchet to activate evolution

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A collaborative work between researchers from the FOM Institute AMOLF (Amsterdam, The Netherlands) and researchers from the LIPhy has evidenced a new mechanism that could activate Darwinian evolution. This mechanism is based on two ingredients : environmental fluctuations and the presence of mutations with tradeoff effects between different environments.

It is usually considered that such mutations constrain Darwinian evolution since their effects in one environment are counterbalanced by their effects in another environment. But paradoxically, the researchers have shown on the contrary that in a fluctuating environment, the tradeoff effects of those mutations can collectively facilitate the evolution of the system. These properties have been demonstrated here in the case of the repressor-operator pair of the lactose operon in the bacteria Escherichia coli.

The widespread occurrence of tradeoff effects and of environmental fluctuations in nature suggests that this “tradeoff ratchet” mechanism could be of general relevance in evolution. Additionally, this mode of evolution in fluctuating environment could have implications in clinical problems such as the treatment of infections with multidrug protocols, or in biotechnological science, where environmental fluctuations could be applied to improve directed evolution techniques.

These results have been published in PNAS.