Journal of Molecular Evolution

, Volume 72, Issue 4, pp 398–412

Insertion Sequence-Driven Evolution of Escherichia coli in Chemostats

Authors

  • Joël Gaffé
    • Laboratoire Adaptation et Pathogénie des MicroorganismesUniversité Joseph Fourier Grenoble 1
    • CNRS UMR5163
  • Christopher McKenzie
    • School of Molecular BioscienceThe University of Sydney
  • Ram P. Maharjan
    • School of Molecular BioscienceThe University of Sydney
  • Evelyne Coursange
    • Laboratoire Adaptation et Pathogénie des MicroorganismesUniversité Joseph Fourier Grenoble 1
    • CNRS UMR5163
  • Tom Ferenci
    • School of Molecular BioscienceThe University of Sydney
    • Laboratoire Adaptation et Pathogénie des MicroorganismesUniversité Joseph Fourier Grenoble 1
    • CNRS UMR5163
Article

DOI: 10.1007/s00239-011-9439-2

Cite this article as:
Gaffé, J., McKenzie, C., Maharjan, R.P. et al. J Mol Evol (2011) 72: 398. doi:10.1007/s00239-011-9439-2

Abstract

Insertion sequence (IS) elements are present in almost all bacterial genomes and are mobile enough to provide genomic tools to differentiate closely related isolates. They can be used to estimate genetic diversity and identify fitness-enhancing mutations during evolution experiments. Here, we determined the genomic distribution of eight IS elements in 120 genomes sampled from Escherichia coli populations that evolved in glucose- and phosphate-limited chemostats by comparison to the ancestral pattern. No significant differential transposition of the various IS types was detected across the environments. The phylogenies revealed substantial diversity amongst clones sampled from each chemostat, consistent with the phenotypic diversity within populations. Two IS-related changes were common to independent chemostats, suggesting parallel evolution. One of them corresponded to insertions of IS1 elements within rpoS encoding the master regulator of stress conditions. The other parallel event was an IS5-dependent deletion including mutY involved in DNA repair, thereby providing the molecular mechanism of generation of mutator clones in these evolving populations. These deletions occurred in different co-existing genotypes within single populations and were of various sizes. Moreover, differential locations of IS elements combined with their transpositional activity provided evolved clones with different phenotypic landscapes. Therefore, IS elements strongly influenced the evolutionary processes in continuous E. coli cultures by providing a way to modify both the global regulatory network and the mutation rates of evolving cells.

Keywords

EvolutionInsertion sequenceTranspositionRearrangementsEscherichia coliGenetic diversityChemostats

Supplementary material

239_2011_9439_MOESM1_ESM.doc (34 kb)
Supplementary material 1 (DOC 34 kb)
239_2011_9439_MOESM2_ESM.xls (128 kb)
Supplementary material 2 (XLS 128 kb)

Copyright information

© Springer Science+Business Media, LLC 2011