Data from: Interaction effects of cell diffusion, cell density and public goods properties on the evolution of cooperation in digital microbes

Microbial cooperation typically consists in the sharing of secreted metabolites (referred to as public goods) within the community. Although public goods generally promote population growth, they are also vulnerable to exploitation by cheating mutants, which no longer contribute, but still benefit from the public goods produced by others. While previous studies have identified a number of key factors that prevent the spreading of cheats, little is known about how these factors interact and jointly shape the evolution of microbial cooperation. Here, we address this issue by investigating the interaction effects of cell diffusion, cell density, public goods diffusion and durability (factors known to individually influence costs and benefits of public goods production) on selection for cooperation. To be able to quantify these effects across a wide parameters space, we developed an individual-based simulation platform, consisting of digital cooperator and cheater bacteria inhabiting a finite continuous two-dimensional toroidal surface. Our simulations, which closely mimic microbial micro-colony growth, revealed that: (a) either reduced cell diffusion (which keeps cooperators together) or reduced public goods diffusion (which keeps the public good closer to the producer) is essential but also sufficient for cooperation to be promoted; (b) the sign of selection for or against cooperation can change as a function of cell density and in interaction with diffusion parameters; and (c) increased public goods durability has opposing effects on the evolution of cooperation depending on the level of cell and public goods diffusion. Our work highlights that interactions among key parameters of public goods cooperation give rise to complex fitness landscapes, a finding that calls for multi-factorial approaches when studying microbial cooperation in natural systems.