Evolution of food preferences drives pleiotropic fitness trade-offs in bacteria

Author(s): Jousset A, Fernkorn F, Lapouge K, Stefan S

Summary:

Bacteria face trade-offs between life history strategies, among which the choice of a generalist or specialist resource use strategy has important effects on fitness. Bacteria bypass this problem by prioritizing nutrient utilisation. They highly specialise on preferred nutrients when available, and invest in a generalist way of life when only second-choice nutrients are left. Here we show that bacteria rapidly evolve new food preferences as an adaptation to a new substrate. We follow the expression of the small regulatory RNA crcZ in Pseudomonas fluorescens which is expressed in absence of preferred resources. It activates the translation of genes involved in alternative resource use. We show that the substrates inhibiting crcZ levels rapidly change when bacteria are confronted with second-choice subtrates, indicating that bacteria evolve new preferences. We further show that these altered food preferences affect the use of complex substrates by bacteria as well as their coexistence with competitors. Evolution of food preferences by bacteria appear therefore as efficient strategy to adapt to new conditions by readjusting the regulation of genes linked to substrate uptake and catabolism.

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