Impact of rheological properties on bacterial streamer formation

Kitamura, Hiroki; Omori, Toshihiro; Ishikawa, Takuji

doi:10.1098/rsif.2021.0546

Cited by 4 publications

(2 citation statements)

References 37 publications

(110 reference statements)

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“…The rheological properties of the biofilm depend on the composition of the extracellular polymeric substances, which, in turn, can vary greatly depending on the microorganisms present, the nutrient availability, and the environmental conditions ( 52 ). The interplay between biofilm rheology and local flow conditions determines biofilm morphology, as recently demonstrated ( 53 ). In particular, our results show that the biofilm’s viscoplastic behavior drives its capability of clogging and forming PFPs in a porous medium, as the rheological descriptors of the biofilm were critical parameters of the mathematical model we developed.…”

Section: Discussionmentioning

confidence: 67%

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

Kurz

Secchi

Carrillo

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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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.

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Section: Discussionmentioning

confidence: 67%

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

Kurz

Secchi

Carrillo

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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“…(2.8) 2.5. Numerical methods The boundary integral equation is calculated by the boundary element method (Pozrikidis 1992), as in our previous paper (Kitamura, Omori & Ishikwa 2021). The spherical surface of each squirmer is discretised by 1280 triangles, and the integration on each triangle is performed by Gaussian quadrature with six Gaussian nodes.…”

Section: Flow-induced Diffusivitymentioning

confidence: 99%

Flow-induced diffusion in a packed lattice of squirmers

Kogure,

Omori,

Ishikawa

2023

J. Fluid Mech.

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Mass transport in suspensions of swimming microorganisms is one of the most important factors for the colonisation and growth of microorganisms. Hydrodynamic interactions among swimming microorganisms play an important role in mass transport, especially in highly concentrated suspensions. To elucidate the influence of highly concentrated cells on mass transport, we numerically simulated mass transport in lattices of squirmers that were fixed in space and oriented in the same direction. The effects of different volume fractions, Péclet numbers ( $Pe$ ) and lattice configurations on mass transport were quantified by tracking Lagrangian material points that move with background flow with Brownian diffusivity. Although the flow field became periodic in space and each streamline basically extended in one direction, the motion of tracer particles became diffusive over long durations due to Brownian motion and cross-flows. Flow-induced diffusion was anisotropic and significantly enhanced over Brownian diffusion in the longitudinal direction. We also investigated mass transport in random configurations of squirmers to reproduce more general conditions. Similar enhanced diffusion was also observed in the random configurations, indicating that the flow-induced diffusion appears regardless of the configurations. The present flow-induced diffusion did not follow $Pe$ dependency of the conventional Taylor dispersion due to the cross-flows. The time and velocity scales were proposed, which enabled us to predict the flow-induced diffusivity from the data of the flow field and Brownian diffusivity without solving the mass conservation equation. The findings reported here improve our understanding of the transport phenomena in packed suspensions of swimming microorganisms.

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50-year History and perspective on biomechanics of swimming microorganisms: Part I. Individual behaviours

Ishikawa

Pedley

2023

Journal of Biomechanics

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Impact of rheological properties on bacterial streamer formation

Cited by 4 publications

References 37 publications

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

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

Flow-induced diffusion in a packed lattice of squirmers

50-year History and perspective on biomechanics of swimming microorganisms: Part I. Individual behaviours

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