Ecological memory of hydrodynamic cues shapes growth and migration of motile microorganisms

TL;DR

This study demonstrates that hydrodynamic cues create a form of ecological memory in motile microorganisms, influencing their growth, migration, and resilience through flow history effects, with implications for understanding microbial responses in dynamic aquatic environments.

Contribution

The paper introduces a mechanistic framework showing how prior fluid flow exposure affects microbial growth and migration, revealing flow-induced ecological memory in motile microbes.

Findings

Hydrodynamic exposure alters microbial doubling time and carrying capacity.

Flow history influences microbial gravitactic stability and swimming speed.

Prior flow exposure shifts growth phase progression and environmental tolerance.

Abstract

Microorganisms live in inherently dynamic environments where fluctuations in biotic and abiotic factors shape their behaviour, physiology, and fitness. The concept of ecological memory: the lasting imprint of prior environmental cues, suggests that past exposures can exert prolonged effects on microbial growth, resilience, and phenotypic expressions. For motile microbes in aquatic ecosystems, environmental variability is mediated by fluid motion, which may engender a form of hydrodynamic memory, whereby prior exposure to specific spatio-temporal cues influence future growth and migratory behaviour. Yet, the emergence of such flow-induced memory, or its long-term consequences for trait evolution and population dynamics, remain unexplored. We integrate millifluidic flow control, high-resolution cell tracking, and tunable hydrodynamic cues to quantify growth and migration of Heterosigma akashiwo, a model microbe, across growth stages. Using two complementary perturbation scenarios: standard (flow after static conditions) and reverse (flow before static growth), we test how the temporal structure of forcing shapes multigenerational responses. This combinatorial design disentangles exposure history from its duration, and reveals how prior flow modulates sensitivity, generating legacy effects. Compared with static controls, repeated hydrodynamic exposure alters doubling time, carrying capacity, gravitactic stability, and swimming speed distributions; shifting growth phase progression and tolerance to subsequent perturbations. These results establish a mechanistic framework for flow-induced memory in motile microbes, revealing how past fluidic cues shape future growth and migration. Our study advances predictive understanding of motile microbes in natural and engineered hydrodynamic systems experiencing increasing variability under global environmental changes.