Directed evolution of Escherichia coli with lower-than-natural plasmid mutation rates

Nucleic Acids Res. 2018 Sep 28;46(17):9236-9250. doi: 10.1093/nar/gky751.


Unwanted evolution of designed DNA sequences limits metabolic and genome engineering efforts. Engineered functions that are burdensome to host cells and slow their replication are rapidly inactivated by mutations, and unplanned mutations with unpredictable effects often accumulate alongside designed changes in large-scale genome editing projects. We developed a directed evolution strategy, Periodic Reselection for Evolutionarily Reliable Variants (PResERV), to discover mutations that prolong the function of a burdensome DNA sequence in an engineered organism. Here, we used PResERV to isolate Escherichia coli cells that replicate ColE1-type plasmids with higher fidelity. We found mutations in DNA polymerase I and in RNase E that reduce plasmid mutation rates by 6- to 30-fold. The PResERV method implicitly selects to maintain the growth rate of host cells, and high plasmid copy numbers and gene expression levels are maintained in some of the evolved E. coli strains, indicating that it is possible to improve the genetic stability of cellular chassis without encountering trade-offs in other desirable performance characteristics. Utilizing these new antimutator E. coli and applying PResERV to other organisms in the future promises to prevent evolutionary failures and unpredictability to provide a more stable genetic foundation for synthetic biology.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Base Sequence
  • DNA Copy Number Variations
  • DNA Polymerase I / genetics*
  • DNA Polymerase I / metabolism
  • DNA Replication
  • DNA, Bacterial / genetics*
  • DNA, Bacterial / metabolism
  • Directed Molecular Evolution / methods*
  • Endoribonucleases / genetics*
  • Endoribonucleases / metabolism
  • Escherichia coli / genetics*
  • Escherichia coli / metabolism
  • Escherichia coli / radiation effects
  • Escherichia coli Proteins / genetics*
  • Escherichia coli Proteins / metabolism
  • Genetic Engineering / methods
  • Mutation Rate
  • Plasmids / chemistry*
  • Plasmids / metabolism
  • Selection, Genetic
  • Sequence Analysis, DNA
  • Synthetic Biology
  • Ultraviolet Rays


  • DNA, Bacterial
  • Escherichia coli Proteins
  • DNA Polymerase I
  • Endoribonucleases
  • ribonuclease E