Microbial Experimental Evolution - a proving ground for evolutionary theory and a tool fordiscovery.

Michael J McDonald

doi:10.15252/embr.201846992

Abstract

Microbial experimental evolution uses controlled laboratory populations to study the mechanisms of evolution. The molecular analysis of evolved populations enables empirical tests that can confirm the predictions of evolutionary theory, but can also lead to surprising discoveries. As with other fields in the life sciences, microbial experimental evolution has become a tool, deployed as part of the suite of techniques available to the molecular biologist. Here, I provide a review of the general findings of microbial experimental evolution, especially those relevant to molecular microbiologists that are new to the field. I also relate these results to design considerations for an evolution experiment and suggest future directions for those working at the intersection of experimental evolution and molecular biology.

Highlights

Experimental studies of evolving populations constitute one of the foundations of the theory of evolution [1]
Studies of microbial populations in the laboratory bring greater power and precision to experimental evolution studies, providing a means to carry out elaborate tests of theory and explore new ideas in evolutionary biology [2]
Experiments show that beneficial mutations engineered into a lowfitness genetic background have a larger effect than if they are engineered into a high-fitness background (Fig 2B)

Summary

Introduction

Experimental studies of evolving populations constitute one of the foundations of the theory of evolution [1]. Instead of throwing out or using all of the resultant population, the experimental evolutionist transfers or dilutes the culture to allow continued growth and division This cycle can be continued indefinitely, and as the generations accumulate, natural selection will drive the population to adapt to the laboratory environment. Experiments show that beneficial mutations engineered into a lowfitness genetic background have a larger effect than if they are engineered into a high-fitness background (Fig 2B) This “diminishing returns” epistasis has been observed using beneficial mutations from the experimental evolution of M. extorquens and S. cerevisiae [25], as well as from the E. coli LTEE [26]. One of the more surprising findings in evolution experiments has been the capacity for these simple experimental systems to evolve diverse, co-existing subpopulations adapted to different niches, evident in both short- and long-term studies of evolution [6,27,28] (Fig 2C). As a consequence of 2 of 14 EMBO reports 20: e46992 | 2019

F Animal model

Findings

D Competetive exclusion