Spatial Structure in Microbial Competition Models

Understanding the structure and behavior of diverse microbial communities is currently a major challenge in the life sciences. The interactions shaping these communities are physical processes, but are often modeled in a mean-field limit that neglects spatial structure. How does spatial structure affect the community-level properties of microbial ecosystems? We have developed a spatial model of two fundamental interactions between microbes: competition for resources and “chemical warfare” via secreted antibiotics. Our group recently showed that a metabolic trade-off constraint in a non-spatial model allows for degenerate steady states with diverse coexisting species. We find that 1D space preserves diversity, but selects a unique steady-state abundance and introduces a new dynamical time scale for relaxation to this steady state. The new time scale characterizes a regime where population dynamics slow down as resource diffusion speeds up. Interestingly, population fluctuations lead to rank-abundance curves that are indistinguishable from neutral and non-spatial models, suggesting a surprising universality at the ecosystem level.