InterPore2021

Pore-scale origin of flow-induced bio-aggregation

31 May 2021, 15:25

15m

Oral Presentation (MS5) Biochemical processes and biofilms in porous media MS5

Speaker

Sang Lee

Description

Microbes in natural and engineering systems are often found as aggregates consisting of microbial communities, organic and inorganic matters, and water. Such bio-aggregates play important roles in shaping biogeochemistry of soil and groundwater environments, clogging of porous media, biofilm formation, and human lung infections [1 – 3]. In addition, aggregated cells are reported to have enhanced protections against external stresses such as anti-biotics, nutrient starvation, oxidative stress, etc., helping microbes to cope with environmental changes [3]. Therefore, understanding how bio-aggregates are formed has been an active area of research in not only engineering and natural sciences but also in clinical and evolutionary standpoints. While bio-aggregates are widely generated in porous systems, the role of pore-scale flow and porous media structure on aggregation is still poorly understood. In this study, we combine microfluidics experiments and three-dimensional (3D) numerical simulations to demonstrate that the unique 3D flow structure at the constriction points of pore-throats, which is ubiquitous in porous media, induces bio-aggregate formation.

We use a single channel with a sinusoidal pore-throat as an analog for a porous system (FIG. 1A). Upon injection of an E. coli suspension (OD600 = 0.1) at a constant flow rate (0.2 μl/min), we observed the formation of bio-aggregates at the pore-throat while in a straight channel only attachment and growth were detected (FIG. 1B - D). Pore clogging and pressure build-up occur as E. coli cells aggregate, which eventually lead to the detachment and flushing of bio-aggregates. A series of laboratory and numerical experiments revealed that 3D secondary flows facilitate attachment and capture of cells at the pore-throat, inducing aggregation. We further identified a critical shear stress value (~ 1.8 Pa) below which an aggregate forms and above which biofilm streamer-like morphology is found. Finally, we show that when the shear stress at the pore-throat is maintained below the critical shear stress, the pore-throat is rapidly clogged by bio-aggregates.

References

[1] P. C. Baveye and C. Darnault, Proc. Natl. Acad. Sci. U. S. A. 114, E2802 (2017).
[2] A. Ebrahimi and D. Or, Glob. Chang. Biol. 22, 3141 (2016).
[3] T. Trunk, H. S. Khalil, and J. C. Leo, AIMS Microbiol. 4, 140 (2018).

Presentation materials

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