Modeling cell-death patterning during biofilm formation

Abstract

Self-organization by bacterial cells often leads to the formation of a highly complex spatially-structured biofilm. In such a bacterial biofilm, cells adhere to each other and are embedded in a self-produced extracellular matrix (ECM). Bacillus substilis bacteria utilize localized cell-death patterns which focuses mechanical forces to form wrinkled sheet-like structures in three dimensions. A most intriguing feature underlying this biofilm formation is that vertical buckling and ridge location is biased to occur in region of high cell-death. Here we present a spatially extended model to investigate the role of the bacterial secreted ECM during the biofilm formation and the self-organization of cell-death. Using this reaction-diffusion model we show that the interaction between the cell's motion and the ECM concentration gives rise to a self-trapping instability, leading to variety of cell-death patterns. The resultant spot patterns generated by our model are shown to be in semi-quantitative agreement with recent experimental observation.

Spreading of nonmotile bacteria on a hard agar plate: Comparison between agent-based and stochastic simulations

“…Similar morphological patterns have also been observed in growing yeast colonies [21]. Several studies [22][23][24][25][26][27][28], since then, have proposed mathematical models to investigate the phase-diagram of Ref. [23].…”

Critical review on biofilm methods

“…This procedure couples green SYTO-9 (cell permeant) and red propidium iodide (cell impermeant) so that bacteria with a compromised membrane appear yellow or red, while the live viable cells appear green. This labeling can be used for example to analyze the spatial distribution of viable bacteria (Hope et al, 2002), observe the existence of localized cell death in biofilms and their regulation (Asally et al, 2012;Ghosh et al, 2013;Guilbaud et al, 2015;Webb et al, 2003), and to assess the effect of several antimicrobials on cell viability (Bridier et al, 2012;Doroshenko et al, 2014;Marchal et al, 2011;Verma et al, 2010). However, CLSM imagining with live/dead staining should be carefully analyzed since differentiation between the red or green channels is often biased by the intensity of the lasers used.…”

Mechanically-driven phase separation in a growing bacterial colony

“…Bacteria are known to selforganize into multicellular communities, commonly known as biofilms, in which microbial cells live in close association with a solid surface or liquid-air interface and are embedded in a self-produced extracellular matrix. Extracellular polymeric substances (EPSs) play an important role in determining the structural and mechanical architecture of a biofilm (7)(8)(9)(10)(11)(12). Generally, the collective dynamics of bacterial colony involves a complex interplay of various physical, chemical, and biological mechanisms, such as growth and differentiation of cells, production of EPSs, the collective movement of cells determined by interacting physical forces and chemical cues, e.g., chemotaxis, motility, cellcell signaling, adhesion, and gene regulation (13)(14)(15)(16)(17)(18)(19).…”