Microbiota dynamics arise from a plethora of interspecies interactions, including resource competition, cross-feeding, and pH modulation. The individual contributions of these mechanisms are challenging to untangle, especially in natural or complex laboratory environments where the landscape of resource competition is unclear.

First, I will discuss how we developed a framework to estimate the extent of multi-species niche overlaps by combining metabolomics data of individual species, growth measurements in pairwise spent media, and mathematical models. When applied to an in vitro model system of human gut commensals in complex media, our framework revealed that a simple model of resource competition described most pairwise interactions. By grouping metabolomic features depleted by the same set of species, we constructed a coarse-grained consumer-resource model that predicted assembly compositions to reasonable accuracy.

Next, I will show how dose dependence can arise between closely related organisms as long as competition is sufficiently intense. Finally, I will discuss our recent efforts to explore spatial variation along the human intestinal tract, and how that informs our understanding of the gut environment.