Apr 27, 2011

Evolutionary dynamics of bacteria in a human host environment

Proceedings of the National Academy of Sciences of the United States of America
Lei YangSøren Molin

Abstract

Laboratory evolution experiments have led to important findings relating organism adaptation and genomic evolution. However, continuous monitoring of long-term evolution has been lacking for natural systems, limiting our understanding of these processes in situ. Here we characterize the evolutionary dynamics of a lineage of a clinically important opportunistic bacterial pathogen, Pseudomonas aeruginosa, as it adapts to the airways of several individual cystic fibrosis patients over 200,000 bacterial generations, and provide estimates of mutation rates of bacteria in a natural environment. In contrast to predictions based on in vitro evolution experiments, we document limited diversification of the evolving lineage despite a highly structured and complex host environment. Notably, the lineage went through an initial period of rapid adaptation caused by a small number of mutations with pleiotropic effects, followed by a period of genetic drift with limited phenotypic change and a genomic signature of negative selection, suggesting that the evolving lineage has reached a major adaptive peak in the fitness landscape. This contrasts with previous findings of continued positive selection from long-term in vitro evolution experiments....Continue Reading

  • References43
  • Citations158

References

Mentioned in this Paper

Genetic Drift
Pseudomonas aeruginosa (antigen)
Genome
Pathogenic Organism
Biological Adaptation
Genetic Pleiotropy
Cystic Fibrosis
Etiology
Phylogeny
Genomics

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