Competition between growth and shear stress drives intermittency in preferential flow paths in porous medium biofilms

Dorothee L. Kurz, Eleonora Secchi, Francisco J. Carrillo, Ian C. Bourg, Roman Stocker, Joaquin Jimenez-Martine

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

Bacteria in porous media, such as soils, aquifers, and filters, often form surface-attached communities known as biofilms. Biofilms are affected by fluid flow through the porous medium, for example, for nutrient supply, and they, in turn, affect the flow. A striking example of this interplay is the strong intermittency in flow that can occur when biofilms nearly clog the porous medium. Intermittency manifests itself as the rapid opening and slow closing of individual preferential flow paths (PFPs) through the biofilm-porous medium structure, leading to continual spatiotemporal rearrangement. The drastic changes to the flow and mass transport induced by intermittency can affect the functioning and efficiency of natural and industrial systems. Yet, the mechanistic origin of intermittency remains unexplained. Here, we show that the mechanism driving PFP intermittency is the competition between microbial growth and shear stress. We combined microfluidic experiments quantifying Bacillus subtilis biofilm formation and behavior in synthetic porous media for different pore sizes and flow rates with a mathematical model accounting for flow through the biofilm and biofilm poroelasticity to reveal the underlying mechanisms. We show that the closing of PFPs is driven by microbial growth, controlled by nutrient mass flow. Opposing this, we find that the opening of PFPs is driven by flow-induced shear stress, which increases as a PFP becomes narrower due to microbial growth, causing biofilm compression and rupture. Our results demonstrate that microbial growth and its competition with shear stresses can lead to strong temporal variability in flow and transport conditions in bioclogged porous media.

Original languageEnglish (US)
Article numbere2122202119
JournalProceedings of the National Academy of Sciences of the United States of America
Volume119
Issue number30
DOIs
StatePublished - Jul 26 2022

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • Bioclogging
  • bacterial biofilms
  • biofilm dynamics
  • biofouling
  • porous medium flow

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