Applied Math Seminar

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Mechanical feedback and pattern formation in growing microbial communities

Speaker: Scott Weady, Center for Computational Biology, Flatiron Institute

Location: Warren Weaver Hall 1302

Date: Friday, January 23, 2026, 2:30 p.m.

Synopsis:

The structure of microbial communities inherently reflects the mechanics of their environment. In particular, mechanical feedback between growth, stress, and transport can drive instabilities and patterning across scales. In this talk, I present a mathematical framework for understanding how mechanical feedback shapes the morphology of growing microbial communities. We first consider a model bacterial colony growing atop a frictional substrate in which individual cell growth and division is inhibited by collective growth-induced stresses. Particle simulations show the spontaneous emergence of concentric ring patterns in cell size, and a multiscale continuum theory linking single-cell stress responses to collective mechanics shows this patterning arises from stress accumulated over many cell cycles. Next, we consider a colony growing atop a viscous fluid and fueled by the consumption of a suspended nutrient. Here fluid flow is generated by both growth-induced stresses at the surface and nutrient-dependent density gradients in the bulk. Reformulating this problem as an integro-differential equation, we establish a condition for the morphological instability of axisymmetric colonies which reveals a competition between stabilizing growth stresses and destabilizing buoyant flows. These results show how mechanical feedback between growth and stress governs the structure and morphology of growing biological systems.