Journal of Molecular Evolution

, Volume 84, Issue 5–6, pp 279–284

Transposable Elements Mediate Adaptive Debilitation of Flagella in Experimental Escherichia coli Populations

  • Gordon R. Plague
  • Krystal S. Boodram
  • Kevin M. Dougherty
  • Sandar Bregg
  • Daniel P. Gilbert
  • Hira Bakshi
  • Daniel Costa
Original Article

Abstract

Although insertion sequence (IS) elements are generally considered genomic parasites, they can mediate adaptive genetic changes in bacterial genomes. We discovered that among 12 laboratory-evolved Escherichia coli populations, three had experienced at least six different IS1-mediated deletions of flagellar genes. These deletions all involved the master flagellar regulator flhDC, and as such completely incapacitate motility. Two lines of evidence strongly suggest that these deletions were adaptive in our evolution experiment: (1) parallel evolution in three independent populations is highly unlikely just by chance, and (2) one of these deletion mutations swept to fixation within ~1000 generations, which is over two million times faster than expected if this deletion was instead selectively neutral and thus evolving by genetic drift. Because flagella are energetically expensive to synthesize and operate, we suspect that debilitating their construction conferred a fitness advantage in our well-stirred evolution experiment. These findings underscore the important role that IS elements can play in mediating adaptive loss-of-function mutations in bacteria.

Keywords

Adaptive evolution Parallel evolution Natural selection Insertion sequence element Loss-of-function mutation Experimental evolution 

Copyright information

© Springer Science+Business Media, LLC 2017

Authors and Affiliations

  • Gordon R. Plague
    • 1
  • Krystal S. Boodram
    • 2
  • Kevin M. Dougherty
    • 3
  • Sandar Bregg
    • 1
    • 4
  • Daniel P. Gilbert
    • 1
    • 5
  • Hira Bakshi
    • 1
  • Daniel Costa
    • 1
    • 6
  1. 1.Department of BiologyState University of New York at PotsdamPotsdamUSA
  2. 2.Simon Gratz High SchoolPhiladelphiaUSA
  3. 3.Kellogg Biological StationMichigan State UniversityHickory CornersUSA
  4. 4.Department of Environmental Health Sciences, School of Public HealthUniversity of MichiganAnn ArborUSA
  5. 5.School of Engineering LabClarkson UniversityPotsdamUSA
  6. 6.Department of Cell BiologyDuke University Medical CenterDurhamUSA

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