Nonlinear competition avoidance favors coexistence in microbial populations

TL;DR

This study introduces a spatial model where nonlinear, density-dependent motility regulation enables competing microbial species to coexist by promoting spatial segregation, counteracting competitive exclusion seen in well-mixed models.

Contribution

The paper develops a minimal spatial model demonstrating how nonlinear motility responses can sustain coexistence in competing microbial populations.

Findings

Nonlinear motility promotes spatial segregation and coexistence.

Emergent patterns include regimes where weaker competitors have higher abundance.

Nonlinear, competitor-induced motility is key to microbial coexistence.

Abstract

Bacteria regulate their motility through a variety of mechanisms, including quorum sensing (QS) and other density-dependent responses mediated by diffusible signals. While nonlinear density-dependent motility is well known in active-matter theory to generate nonequilibrium spatial patterns, its consequences for the coexistence of growing, interacting species remain less explored. Here we develop a minimal spatially structured model for two strongly competing species in which local demographic interactions are coupled to an escape response: each species increases its motility nonlinearly (sigmoidal) with the local abundance of its competitor. We show that this sigmoidal motility regulation promotes optimal spatial self-organization and can sustain long term coexistence via segregation, even in parameter regimes that yield competitive exclusion in well-mixed Lotka-Volterra dynamics. On two-dimensional lattices, the interplay between demographic competition and density-dependent motility generates a range of emergent patterns, including regimes in which the weaker competitor counterintuitively has higher total abundance. Overall, our results identify nonlinear, competitor-induced motility as a fundamental mechanism capable of sustaining coexistence in competing microbial populations.