Neutral Diversity in Experimental Metapopulations

TL;DR

This paper models neutral genetic diversity in experimental bacterial populations using coalescent theory, revealing optimal dilution factors, mutation spectrum behaviors, and divergence patterns relevant for phenotype selection.

Contribution

It introduces a coalescent-based model for neutral diversity in serially transferred bacterial populations, including effects of extinction, splitting, and mutation sharing.

Findings

Optimal dilution factor maximizes neutral diversity.

Mutation frequency spectrum follows a power-law under certain regimes.

New formula for shared and private mutations between split populations.

Abstract

New automated and high-throughput methods allow the manipulation and selection of numerous bacterial populations. In this manuscript we are interested in the neutral diversity patterns that emerge from such a setup in which many bacterial populations are grown in parallel serial transfers, in some cases with population-wide extinction and splitting events. We model bacterial growth by a birth-death process and use the theory of coalescent point processes. We show that there is a dilution factor that optimises the expected amount of neutral diversity for a given amount of cycles, and study the power law behaviour of the mutation frequency spectrum for different experimental regimes. We also explore how neutral variation diverges between two recently split populations by establishing a new formula for the expected number of shared and private mutations. Finally, we show the interest of such a setup to select a phenotype of interest that requires multiple mutations.