(186f) The Benefits of Resource Partitioning and Division of Labor in Biofilm Based Microbial Consortia

Microbial consortia are commonly observed in natural and synthetic systems, and these consortia frequently result in higher biomass production relative to monocultures. The focus here is on the impact of initial spatial localization and substrate diffusivity on the growth of a model microbial consortium consisting of two different producer strains that consumes glucose and produce acetate or lactate and a scavenger strain that consumes the acetate and lactate. The mathematical model is based on an individual cell model where growth is described by Monod kinetics, and substrate transport is described by a continuum-based, non-equilibrium reaction-diffusion model where convective transport is negligible (e.g., in a biofilm). The impact of the initial population density and substrate diffusivity is examined in different systems. Depending on the geometry of the system, transitions are observed from the highest initial density resulting in the greatest cell growth to cell growth being independent of initial density. A high initial density minimizes diffusive transport time and is typically expected to result in the highest growth, but this expected behavior is not predicted in environments with lower diffusivity or larger length scales. For example, when the producer cells are placed on the bottom of the domain with the scavenger cells above in a layered biofilm arrangement, a critical transition is observed from a thin, dense initial scavenger layer is optimal for cell growth at the highest diffusivities to a thicker, less dense initial scavenger layer providing maximal growth at lower diffusivities. The overall conclusion is that high density clustering of members of a food chain is optimal under most common transport conditions, but under some slow transport conditions, high density clustering may not be optimal for microbial growth.