Cross-feeding shapes both competition and cooperation in microbial ecosystems

TL;DR

This paper analytically explores how cross-feeding influences competition and cooperation in microbial ecosystems, revealing new bounds and relationships that shape community properties.

Contribution

It introduces a mean-field analytical solution to the Microbial Consumer Resource Model, providing new insights into species-packing, richness, and resource abundance in cross-feeding ecosystems.

Findings

Derived species-packing bounds for diverse ecosystems with cross-feeding.

Provided simple expressions for species richness and secreted resource abundance.

Showed the interplay of competition and cooperation shapes microbial community properties.

Abstract

Recent work suggests that cross-feeding -- the secretion and consumption of metabolic biproducts by microbes -- is essential for understanding microbial ecology. Yet how cross-feeding and competition combine to give rise to ecosystem-level properties remains poorly understood. To address this question, we analytically analyze the Microbial Consumer Resource Model (MiCRM), a prominent ecological model commonly used to study microbial communities. Our mean-field solution exploits the fact that unlike replicas, the cavity method does not require the existence of a Lyapunov function. We use our solution to derive new species-packing bounds for diverse ecosystems in the presence of cross-feeding, as well as simple expressions for species richness and the abundance of secreted resources as a function of cross-feeding (metabolic leakage) and competition. Our results show how a complex interplay between competition for resources and cooperation resulting from metabolic exchange combine to shape the properties of microbial ecosystems.