EESS seminar talk on "Dynamic microbial interactions and coexistence in changing environments"

Bacterial communities play central roles across natural and engineered systems, contributing to processes ranging from biogeochemical cycling to human health and environmental management. Within these systems, microbial communities shape and are shaped by their environment through the exchange of metabolites, signaling molecules, and other bioactive compounds. By modifying their local environment, microbes continuously alter the conditions that define how they interact, creating a dynamic feedback between community activity and environmental state. Yet, so far many studies inferred microbial interactions from endpoint outcomes, leaving dynamics of these feedbacks largely unresolved.
In this talk, I will present recent work using high-throughput, time-resolved microdroplet approaches to quantify how bacterial interactions emerge and change across environmental conditions. By tracking the dynamics of interacting populations, we find that interactions are inherently dynamic, shifting between competitive, neutral, and beneficial over ecological timescales. These shifts follow characteristic trajectories that depend on the metabolic context and can be linked to underlying resource dynamics.
Building on this, we find that such temporally structured interaction dynamics can contribute to stable coexistence of bacteria, for example through shifts in resource use and environmental modification that enable niche partitioning over time. Together, this work aims to move towards a more mechanistic understanding of how metabolic interactions and environmental feedbacks shape both interaction dynamics and community stability, with implications for microbial processes across natural and engineered systems.

Dr. Anna Weiss is a microbial ecologist and currently a postdoctoral researcher at ETH Zürich and Eawag, where she investigates how microbial interactions shape community function and robustness. Trained at the interface of physics and microbiology, her work combines synthetic bacterial communities, microfluidics, and single-cell approaches with ecological theory to uncover the mechanisms underlying interaction networks and functional robustness in microbiomes. She is a Walter Benjamin Fellow of the DFG and is particularly interested in linking ecological principles to experimentally tractable microbial systems across environments.