Cell motility enhances metabolic coupling in spatially structured microbial communities

Metabolic interactions are central to the functioning of microbial communities. In spatially structured environments, such interactions typically require close physical proximity between partner cells. However, cell division drives spatial segregation of interaction partners, as the cells emerging from division remain adjacent and form clonal clusters, weakening these interactions. Here, we hypothesized that active cell motility can reduce this spatial segregation by enabling cells to leave clonal clusters and thereby enhance metabolic interactions. We tested this hypothesis by performing time-lapse single-cell imaging of a synthetic cross-feeding consortium growing in microfluidic chambers. We found that surface motility disrupted clonal clustering, enhanced spatial intermixing, and consequently increased the growth rates of individual cells and community productivity. Individual-based simulations further revealed that this effect is robust across motility modes and a wide range of ecological and physiological parameters. Together, our findings demonstrate that even non-directed, random motility, without chemotactic sensing, is sufficient to enhance metabolic interactions by separating cells from their clonal lineages and repositioning them in proximity to their metabolic partners, thereby acting as a key driver of community functioning in spatially structured microbial systems.