Costs and Benefits of High Mutation Rates: Adaptive Evolution of Bacteria in the Mouse Gut

  1. Antoine Giraud1,2,
  2. Ivan Matic1,
  3. Olivier Tenaillon1,
  4. Antonio Clara2,
  5. Miroslav Radman1,
  6. Michel Fons2,
  7. François Taddei1,*

+ Author Affiliations

  1. 1 E9916, Institut National de la Santé et de la Recherche Médicale, Faculté de Médicine “Necker Enfants Malades,” Université RenéDescartes-Paris V, 156 Rue de Vaugirard, 75015 Paris, France.
  2. 2 UEPSD-FBI, Bat 440-CRJ, Institut National de la Recherche Agronomique, 78352 Jouy-en-Josas, France.


We have shown that bacterial mutation rates change during the experimental colonization of the mouse gut. A high mutation rate was initially beneficial because it allowed faster adaptation, but this benefit disappeared once adaptation was achieved. Mutator bacteria accumulated mutations that, although neutral in the mouse gut, are often deleterious in secondary environments. Consistently, the competitiveness of mutator bacteria is reduced during transmission to and re-colonization of similar hosts. The short-term advantages and long-term disadvantages of mutator bacteria could account for their frequency in nature.

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  • Received for publication 9 October 2000.
  • Accepted for publication 2 February 2001.