Trade-offs Between Growth and Adaptation in Spatially Structured Bacterial Populations

The availability of nutrients and environmental constraints influence bacterial growth in natural environments. Spatial structure, fluid flow, and nutrient consumption generate microgradients that drive uneven colony expansion and modulate local growth rates. Bacteria adapt to multiple carbon sources through co-utilization or hierarchical consumption, the latter producing lag phases- non growing adaptation phases-whose duration depends on nutrient composition and strain. While extensively studied, lag phases have been mostly investigated in the temporal domain, neglecting their spatial dimension.

Here we examine how nutrient microgradients, lag phases, and spatial constraints interact to shape bacterial growth in non–well-mixed environments. We developed a physical model describing the diffusion and hierarchical uptake of carbon sources in a spatially structured population. The model predicts a trade-off between growth on less favourable nutrients—driven by gradients—and the duration of lag phases, which together control population-level dynamics.

Microfluidic experiments with E. coli monolayers under controlled carbon influx and confinement confirmed the model predictions, revealing how nutrient gradients influence adaptation. Thanks to single-cell imaging and analysis, these results provide a quantitative framework for understanding microbial growth in structured environments and the ecological relevance of nutrient hierarchies.