Alternative stable states in a model of microbial community limited by multiple essential nutrients

TL;DR

This paper models microbial communities with multiple essential nutrients, revealing numerous stable states and complex regime shifts driven by nutrient influxes, using game theory to predict community configurations.

Contribution

Introduces a novel model of microbial multistability considering multiple nutrients and applies game theory to predict stable states based on species' competitive abilities.

Findings

Exponential number of potential stable states identified.

Multiple uninvadable stable states exist for given nutrient conditions.

Discontinuous regime shifts occur during community assembly and nutrient changes.

Abstract

Microbial communities routinely have several alternative stable states observed for the same environmental parameters. Sudden and irreversible transitions between these states make external manipulation of these systems more complicated. To better understand the mechanisms and origins of multistability in microbial communities, we introduce and study a model of a microbial ecosystem colonized by multiple specialist species selected from a fixed pool. Growth of each species can be limited by essential nutrients of two types, e.g. carbon and nitrogen, each represented in the environment by multiple metabolites. We demonstrate that our model has an exponentially large number of potential stable states realized for different environmental parameters. Using game theoretical methods adapted from the stable marriage problem we predict all of these states based only on ranked lists of competitive abilities of species for each of the nutrients. We show that for every set of nutrient influxes, several mutually uninvadable stable states are generally feasible and we distinguish them based upon their dynamic stability. We further explore an intricate network of discontinuous transitions (regime shifts) between these alternative states both in the course of community assembly, or upon changes of nutrient influxes.