Genetic interfaces at the frontier of expanding microbial colonies

TL;DR

This paper investigates the behavior of genetic interfaces in expanding microbial colonies, revealing how geometric effects and fluctuations influence interface width and stability at the colony frontier.

Contribution

It uncovers the role of geometric focusing and fluctuations in controlling genetic interface width in microbial colonies, especially at the frontier.

Findings

Genetic interface width saturates at finite values over time.

Interface dynamics are influenced by colony frontier curvature.

Numerical simulations show a logarithmic relationship between interface width and fluctuations.

Abstract

We study the genetic interfaces between two species of an expanding colony that consists of individual microorganisms that reproduce and undergo diffusion, both at the frontier and in the interior. Within the bulk of the colony, the genetic interface is controlled in a simple way via interspecies interactions. However, at the frontier of the colony, the genetic interface width saturates at finite values for long times, both for neutral strains and interspecies interactions such as antagonism. This finite width arises from geometric effects: genetic interfaces drift toward local minima at an undulating colony frontier, where a focusing mechanism induced by curvature impedes diffusive mixing. Numerical simulations support a logarithmic dependence of the genetic interface width on the strength of the number fluctuations.