Diffusible Public Goods in Microbial Communities: Understanding Spatial Dynamics and Implications for Antibiotic Resistance

Microbial ecological interactions are often mediated by the production, secretion, and uptake of metabolites which act as ‘diffusible public goods. Neighboring organisms can potentially benefit from the conferred fitness advantage of the public good without incurring the cost of production. Determining the interaction range of diffusible public goods in spatially structured microbial communities can help us forecast evolutionary and ecological dynamics. With this perspective in hand, we study the outcome of diffusible public goods games in the context of a spatially structured resistant-susceptible microbial community exposed to an antibiotic gradient where the resistant strategy produces and secretes a diffusible public good capable of protecting the susceptible strategy. Motivated by recent studies that show a simple uptake and leak model leads to the emergence of a local interaction range, we use agent based simulations and microfluidic experiments to explore biologically relevant parameter space to predict dynamics as they apply to antibiotics and diffusible public goods. For instance, beta-lactam resistant bacteria are known to produce beta-lactamase enzymes that neutralize the beta-lactam. These enzymes, created internally, can diffuse outside of the cell, offering protection to nearby non-producers. The presence of such diffusible public goods in microbial systems can foster intricate relationships, even leading to co-dependent microbial consortia. Grasping these dynamics is crucial for a comprehensive understanding of antibiotic resistance.