Evolvability and hierarchy in rewired bacterial gene networks

Nature. 2008 Apr 17;452(7189):840-5. doi: 10.1038/nature06847.


Sequencing DNA from several organisms has revealed that duplication and drift of existing genes have primarily moulded the contents of a given genome. Though the effect of knocking out or overexpressing a particular gene has been studied in many organisms, no study has systematically explored the effect of adding new links in a biological network. To explore network evolvability, we constructed 598 recombinations of promoters (including regulatory regions) with different transcription or sigma-factor genes in Escherichia coli, added over a wild-type genetic background. Here we show that approximately 95% of new networks are tolerated by the bacteria, that very few alter growth, and that expression level correlates with factor position in the wild-type network hierarchy. Most importantly, we find that certain networks consistently survive over the wild type under various selection pressures. Therefore new links in the network are rarely a barrier for evolution and can even confer a fitness advantage.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Escherichia coli / genetics*
  • Escherichia coli / growth & development
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism
  • Evolution, Molecular*
  • Gene Expression Regulation, Bacterial / genetics*
  • Gene Regulatory Networks / genetics*
  • Genes, Bacterial / genetics
  • Genetic Engineering*
  • Heat-Shock Response
  • Oligonucleotide Array Sequence Analysis
  • Open Reading Frames / genetics
  • Promoter Regions, Genetic / genetics
  • Selection, Genetic*
  • Serial Passage
  • Sigma Factor / genetics
  • Sigma Factor / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / metabolism


  • Escherichia coli Proteins
  • Sigma Factor
  • Transcription Factors