Spatial organization of biomass controls intrinsic permeability of porous systems

TL;DR

This study reveals that the spatial arrangement of microbial biomass in porous media, influenced by motility, critically determines permeability changes, with a new mechanistic model predicting flow resistance based on biomass distribution.

Contribution

It introduces a mechanistic model linking biomass spatial organization to permeability, highlighting motility's role in controlling flow resistance in biofilms.

Findings

Motile bacteria cause less permeability reduction than non-motile bacteria despite similar biomass.

Biomass spatial distribution, not total biomass, primarily controls permeability.

Developed a model predicting permeability from pore-scale biomass patterns.

Abstract

Biofilms in porous media critically influence hydraulic properties in environmental and engineered systems. However, a mechanistic understanding of how microbial life controls permeability remains elusive. By combining microfluidics, controlled pressure gradient and time-lapse microscopy, we quantify how motile and non-motile bacteria colonize a porous landscape and alter its resistance to flow. We find that while both strains achieve nearly identical total biomass, they cause drastically different permeability reductions - 78% for motile cells versus 94% for non-motile cells. This divergence stems from motility, which limits biomass spatial accumulation, whereas non-motile cells clog the entire system. We develop a mechanistic model that accurately predicts permeability dynamics from the pore-scale biomass distribution. We conclude that the spatial organization of biomass, not its total amount, is the primary factor controlling permeability.