Antimicrobial resistance to drugs (AMR), a global threat to human and animal health, is often regarded as a result of microbial cooperation, leading to the coexistence of drug-resistant and drug-sensitive cells in large communities and static environments. This picture is, however, greatly altered by the fluctuations arising in volatile environments, in which microbial communities commonly evolve. Motivated by the need to better understand the `eco-evolution' of cooperative AMR, we study a population of time-varying size consisting of two competing strains: resistant versus sensitive microbes. We model the time-fluctuating environment as random switches between states of nutrient abundance and scarcity, which can cause population bottlenecks. The eco-evolutionary dynamics of cooperative AMR is thus characterised by demographic noise (microbial birth and death events) coupled to environmental fluctuations. In the first part of the talk, I will focus on well-mixed microbial populations. Using computational and analytical means, I will discuss the environmental conditions for the long-lived coexistence or fixation of both strains, and characterise a fluctuation-driven AMR eradication mechanism where resistant microbes experience bottlenecks leading to extinction. In the second part of the talk, I will extend the above results to spatially structured microbial metapopulations, modelled by a 2D square lattice with migration across adjacent populations.
