Modeling of Mesoscale Variability in Biofilm Shear Behavior

Abstract

Formation of bacterial colonies as biofilm on the surface/interface of various objects has the potential to impact not only human health and disease but also energy and environmental considerations. Biofilms can be regarded as soft materials, and comprehension of their shear response to external forces is a key element to the fundamental understanding. A mesoscale model has been presented in this article based on digitization of a biofilm microstructure. Its response under externally applied shear load is analyzed. Strain stiffening type behavior is readily observed under high strain loads due to the unfolding of chains within soft polymeric substrate. Sustained shear loading of the biofilm network results in strain localization along the diagonal direction. Rupture of the soft polymeric matrix can potentially reduce the intercellular interaction between the bacterial cells. Evolution of stiffness within the biofilm network under shear reveals two regimes: a) initial increase in stiffness due to strain stiffening of polymer matrix, and b) eventual reduction in stiffness because of tear in polymeric substrate.

Nonlinear rheological characteristics of single species bacterial biofilms

“…Another complexity arises from the fact that extracellular polymers of biofilms are a mixture of multiple polymers; which could interact amongst themselves. In addition, shear forces play an implicit role in shaping the structure of biofilms, the constituent polymeric molecules in the matrix can stretch, reorienting the cells thereby causing local ordering 85,86 . Beyond a certain limit of shear forces, the structures can rupture forming clusters and the clusters can hydro-dynamically interact with each other.…”

A Keystone Methylobacterium Strain in Biofilm Formation in Drinking Water

“…Both modelling [66,67] and experimental studies [57,68] have revealed the important roles that, for example, shear-stress-induced detachment of cells or increased oxygen transport to a biofilm in turbulent flow conditions play on the structure and growth of an established biofilm. From an engineering perspective, this does give some inkling of ways of managing the flow of the water distribution system to control the sloughing of biofilm material into the bulk water that ultimately emerges at the tap.…”

Failure through expanding voids in bacterial streamers

“…The broad reason for initial resistance to crack growth likely shares its physical origin to polymeric composite materials which results in overall similar behavior between LTF and STF behavior [18][19][20] . However, lack of clear trends in STF may indicate that these streamers may have much higher heterogeneity in their structure leading to more flaws which precipitate the fracture early in their life.…”