Joint environmental and demographic fluctuations shape the fate of cooperative antimicrobial resistance #

Lluís Hernández-Navarro, Asker, Matthew, Rucklidge, Alastair M, Mobilia, Mauro

13:50 Tuesday in 3Q68.

Part of the Biofilms and pattern formation session.

Abstract #

Microorganisms live in ecologically dynamic environments that fluctuate between mild and harsh conditions. Critically, the latter gives rise to higher demographic noise and random extinctions that govern evolutionary dynamics, which in turn might shape the environmental conditions through large-scale feedback loops. Although the independent contributions of environmental variability (EV) and demographic fluctuations (DF) have been extensively studied, the emerging eco-evo dynamics' resulting from their joint interplay remains largely unknown due to its challenging complexity and interdisciplinary nature, and poses an open problem that is crucial for many relevant, real world living systems. In this study we focus on the eco-evo dynamics of AntiMicrobial Resistance (AMR), which currently causes approx. 7·10^5 deaths every year, and is estimated to cause 10 million yearly deaths by 2050 [ONeill2016Tackling]. AMR is typically characterized by cooperative behavior: a mutant strain generates a Public Good (PG; e.g., extracellular enzyme) at some metabolic cost (reduced birth rate) and the PG inhibits the antimicrobial drug for all the population (antimicrobial-independent rates for all strains). Furthermore, and grounding on the experimental work of Sanchez and Gore [Sanchez2013Feedback], PG is effectively shared only when the density of cooperators N_c overcomes a given threshold N_c>N_th. Below N_th the Good is held private, within cooperators' intracellular medium, and non-PG-producers become vulnerable to antimicrobial drugs. We will thus assess the AMR eco-evo dynamics of a well-mixed, finite microbial population of fluctuating size composed of a cooperative, PG-producer strain and a free-rider’, defector strain. We will discuss the resulting behaviour that arises from the direct coupling between the evolutionary state (level of cooperation) and the environmental condition (active/inhibited antimicrobial drug for defectors). And, finally, we will show that the previous coupling either enhances species coexistence, extinction of the sensitive strain, or eradication of the resistant microbes depending on the specific environmental statistics.