Environmental Science and Engineering Seminar

Microbial communities in subsurface environments, including soils and aquifers, experience dynamic fluid flow regimes and highly heterogeneous geochemical landscapes. This intricate abiotic–biotic interplay is fundamental to biogeochemical cycling and has critical implications for processes such as bioremediation and biomineralization. To disentangle these interactions, we have developed methodologies that enable investigations at both the single-cell and community scales. At the single-cell level, we examined how chemotactic bacteria respond to nutrient heterogeneity, demonstrating that chemotaxis enhances bacterial colocalization with nutrient hotspots, though this effect is modulated by physical heterogeneity and flow velocity gradients. At the community scale, we uncovered how microbial growth-driven biofilm formation progressively alters the porous medium structure, leading to the emergence of preferential flow paths that exhibit intermittent opening and closure. We mechanistically linked this phenomenon to the dynamic balance between microbial proliferation and shear-induced biofilm detachment. Additionally, we provide the first characterization of permeability heterogeneity within biofilms, a key factor governing solute transport and microbially mediated reactions. These findings offer new insights into microbial dynamics in complex ecosystems and have broad implications for subsurface biogeochemical processes.