Population genetics in microchannels

TL;DR

This study explores how spatial constraints in microchannels influence microbial evolution, revealing rapid diversity loss within lanes and the emergence of stripe patterns, with implications for understanding evolution in confined spaces.

Contribution

The paper introduces a population model for bacteria in microchannels, predicting pattern formation and mutation fixation, supported by experimental validation.

Findings

Diversity is rapidly lost within lanes but persists among lanes.

E. coli organize into stripe patterns over a few generations.

Mutations in the middle of the channel are more likely to fix.

Abstract

Spatial constraints such as rigid barriers affect the dynamics of cell populations, potentially altering the course of natural evolution. In this paper, we investigate the population genetics of Escherichia coli proliferating in microchannels with open ends. Our analysis is based on a population model in which reproducing cells shift entire lanes of cells towards the open ends of the channel. The model predicts that diversity is lost very rapidly within lanes, but at a much slower pace among lanes. As a consequence, two mixed, neutral E. coli strains competing in a microchannel must organize into an ordered regular stripe pattern in the course of a few generations. These predictions are in quantitative agreement with our experiments. We also demonstrate that random mutations appearing in the middle of the channel are much more likely to reach fixation than those occurring elsewhere. Our results illustrate fundamental mechanisms of microbial evolution in spatially confined space.