Phenotypic switching can speed up biological evolution of microbes

TL;DR

This paper demonstrates through computational modeling that stochastic phenotype switching can significantly accelerate microbial adaptation in static environments by allowing populations to bypass fitness valleys and develop beneficial mutations faster.

Contribution

It introduces a novel perspective that phenotype switching can speed up evolution in microbes, especially in the presence of deleterious mutations, with implications for antibiotic resistance.

Findings

Switching to higher fitness phenotypes speeds up adaptation.

Phenotype switching reduces time to develop resistance by bypassing fitness valleys.

Implications for understanding antibiotic resistance emergence.

Abstract

Stochastic phenotype switching has been suggested to play a beneficial role in microbial populations by leading to the division of labour among cells, or ensuring that at least some of the population survives an unexpected change in environmental conditions. Here we use a computational model to investigate an alternative possible function of stochastic phenotype switching - as a way to adapt more quickly even in a static environment. We show that when a genetic mutation causes a population to become less fit, switching to an alternative phenotype with higher fitness (growth rate) may give the population enough time to develop compensatory mutations that increase the fitness again. The possibility of switching phenotypes can reduce the time to adaptation by orders of magnitude if the "fitness valley" caused by the deleterious mutation is deep enough. Our work has important implications for the emergence of antibiotic-resistant bacteria. In line with recent experimental findings we hypothesise that switching to a slower growing but less sensitive phenotype helps bacteria to develop resistance by exploring a larger set of beneficial mutations while avoiding deleterious ones.