Disruption of cross-feeding interactions by invading taxa can cause invasional meltdown in microbial communities

Abstract

<jats:title>Abstract</jats:title><jats:p>The strength of biotic interactions within an ecological community affects the susceptibility of the community to invasion by introduced taxa. In microbial communities, cross-feeding is a widespread type of biotic interaction that has the potential to affect community assembly and stability. Yet, there is little understanding of how the presence of cross-feeding within a community affects invasion risk. Here, I develop a metabolite-explicit model where native microbial taxa interact through both cross-feeding and competition for metabolites. I use this model to study how the strength of biotic interactions, especially cross-feeding, influence whether an introduced taxon can join the community. I found that stronger cross-feeding and competition led to much lower invasion risk, as both types of biotic interactions lead to greater metabolite scarcity for the invader. I also evaluated the impact of a successful invader on community composition and structure. The effect of invaders on the native community was greatest at intermediate levels of cross-feeding; at this “critical” level of cross-feeding, successful invaders generally causing decreased diversity, decreased productivity, greater metabolite availability, and decreased quantities of metabolites exchanged among taxa. Furthermore, these changes resulting from a successful primary invader made communities further susceptible to future invaders. The increase in invasion risk was greatest when the network of metabolite exchange between taxa was minimally redundant. Thus, this model demonstrates a case of invasional meltdown that is mediated by initial invaders disrupting the metabolite exchange networks of the native community.</jats:p>

Non‐zero‐sum microbiome immune system interactions

“…Defining a healthy microbiome is a long-term goal of the field of microbiome research and will require to model the dynamics underpinning the seemingly endless compositional variability between individ-uals. Existing models of microbiome ecology successfully describe select aspects of bacteria-to-bacteria interactions by mapping limits of selfish behavior in a network [200], modeling an effect of the ratio of cooperative to competitive interactions on diversity and stability [201], applying game theory to metabolic interdependencies between microbes [15] and strategies of nutrients utilization [202], calculating an effect of cross-feeding on colonization resistance [203], studying the relationship between nutrients availability and diversity [204], and defining rules of assembly of infant microbiome [205]. However, by design these models are limited to bacteria-to-bacteria interactions.…”

Niche separation in cross-feeding sustains bacterial strain diversity across nutrient environments and may increase chances for survival in nutrient-limited leaf apoplasts

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