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Related Experiment Videos

Adaptive evolution that requires multiple spontaneous mutations: mutations involving base substitutions.

B G Hall1

  • 1Biology Department, University of Rochester, NY 14627.

Proceedings of the National Academy of Sciences of the United States of America
|July 1, 1991
PubMed
Summary
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Adaptive mutations in Escherichia coli

Area of Science:

  • Microbial genetics
  • Molecular evolution

Background:

  • Adaptive mutations can arise in bacterial operons.
  • Previous studies identified adaptive missense mutations in the trp operon of Escherichia coli.

Purpose of the Study:

  • To investigate the frequency and mechanisms of adaptive mutations requiring multiple genetic changes.
  • To determine if existing models explain the observed mutation rates.

Main Methods:

  • Experimental evolution of Escherichia coli under selection pressure.
  • Mutation rate analysis for single and multiple mutations.
  • DNA sequencing of revertant strains.

Main Results:

  • A strain with missense mutations in trpA and trpB reverted to Trp+ 10^8 times more frequently than expected for independent events.

Related Experiment Videos

  • Neither classical spontaneous mutation models nor current adaptive mutation models fully explain the observed double mutation rate.
  • Sequencing revealed specific genetic information in double revertants.

    • Conclusions:

    • Adaptive mutations can facilitate the rapid emergence of advantageous phenotypes requiring multiple genetic alterations.
    • The observed high frequency of multiple adaptive mutations suggests mechanisms beyond independent spontaneous events.
    • Further research is needed to elucidate the mechanistic basis of these accelerated adaptive mutation events.