How adaptation to food resources and death rates shape oscillatory dynamics in a microbial population

TL;DR

This study introduces a consumer-resource model for microbial populations that explains how adaptation and death rates influence oscillatory dynamics, highlighting the importance of timescale interactions and environmental complexity.

Contribution

It presents a minimalistic consumer-resource model revealing the conditions under which microbial populations exhibit oscillations based on adaptation and death timescales.

Findings

Decaying oscillations occur when adaptation timescale exceeds death timescale.

Necromass recycling and multiple food sources affect oscillation parameters.

Facilitating growth reduces the likelihood of oscillations.

Abstract

Microbes constantly interact with their environment by depleting and transforming food sources. Theoretical studies have mainly focused on Lotka-Volterra models, which do not account for food source dynamics. In contrast, consumer-resource models, which consider food source dynamics, are less explored. In particular, it is still unclear what physical mechanisms control oscillatory dynamics at a single population level, a phenomenon which can only be captured by a consumer-resource model. Here, we present a minimalistic consumer-resource model of a single microbial population with growth and death dynamics, consuming a continuously replenishing substrate. Our model reveals that decaying oscillations can occur around steady state if and only if the timescale of microbial adaptation to food supply changes exceeds the death timescale. This interplay of timescales allows us to rationalize the emergence of oscillatory dynamics when adding various biophysical ingredients to the model. We find that microbial necromass recycling or complementary use of multiple food sources reduces the parameter range for oscillations and increases the decay rate of oscillations. Requiring multiple simultaneous food sources has the opposite effect. Essentially, facilitating growth reduces the likelihood of oscillations around a fixed point. We further demonstrate that such damped oscillatory behavior is correlated with persistent oscillatory behavior in a noisy environment. We hope our work will motivate further investigations of consumer-resource models to improve descriptions of environments where food source distributions vary in space and time.