Contrary to the traditional view of bacteria as unicellular organisms, they often communicate with each other, cooperate, and organize themselves into multicellular structures such as biofilms. In our group we use mathematical modeling to investigate two ways in which bacteria cooperate to achieve multicellularity in biofilms: cell–cell signaling through diffusing molecules, and evaporation-driven transport of resources [1] and waste products including ions, nutrients, and metabolic byproducts.
Cell–Cell Signalling in Bacterial Communities
One project investigates how Bacillus subtilis bacteria sense and respond to their local cellular environment through the secretion and import of small diffusible peptides. Using microfluidic chambers and agent-based simulations of 2D bacterial monolayers, we model how signaling molecules diffuse through the extracellular space and regulate gene expression in neighboring cells. Simulations are quantitatively compared to experimental data, showing that diverse collective behaviors, ranging from basic monotonic responses to bistable switches, can emerge from simple diffusion-mediated interactions between cells.
Evaporation-Driven Transport Processes in Biofilms
Bacillus subtilis biofilms can develop a characteristic wrinkled surface during growth, beneath which water channels are formed. Due to evaporation at the biofilm surface, a pressure drop can arise within the biofilm structure, driving a water flux toward the central biofilm region, with radial inflow from the outer parts of the biofilm. To understand these specific hydrodynamic conditions and their impact on the bacteria, the resulting concentration profiles need to be calculated.
Does the continuous channel flux lead to an accumulation of metabolic end products or metal ions? Are observed metal ion distributions caused purely by the hydrodynamic conditions, or is a more complex ECM binding process involved? We aim to answer these questions using numerical simulations, modelling both entire biofilms and specific biofilm regions.
Some references
- L. Chai, V. Zaburdaev, & R. Kolter, How bacteria actively use passive physics to make biofilms, Proc. Natl. Acad. Sci. U.S.A. 121 (40) e2403842121, https://doi.org/10.1073/pnas.2403842121 (2024).