Life on a Surface: Spatial Structure in Microbial Communities

Most studies of the gut microbiota are conducted in well-mixed liquid cultures, yet this model diverges from the true environment of the colon, which is densely packed and relatively solid. In such structured environments, stable spatial structures emerge, enabling interactions such as horizontal gene transfer, type VI secretion, and biofilm formation that are less prevalent in liquid culture. To understand how spatial structure shapes microbial community ecology, we studied communities grown on surfaces.

First, we compared surface-grown and liquid-grown communities to test whether spatial degrees of freedom affect the determinism and stability of community composition. Next, we examined how surface growth influences diversity, asking whether spatial structure allows communities to circumvent the competitive exclusion principle, as observed in macroecological systems. Finally, we evaluated whether consumer-resource models that successfully predict community composition in liquid culture can also capture the behavior of spatially structured communities, both globally and across spatial subsamples.

Together, these results bring microbiome research one step closer to physiological reality and reveal the rules governing microbial community assembly and coexistence within spatially structured systems.