Study Finds Cell Crowding Triggers Unexpected Growth Patterns

A study published in Physical Review Letters on October 10 spells out how cells respond to overcrowding. Researchers from the Flatiron Institute and Purdue University discovered that bacterial cells under physical stress from neighboring cells dramatically slow their growth, resulting in striking concentric circle patterns.

Led by Scott Weady, the team used simulations and modeling to investigate cell proliferation in growing bacterial colonies. They observed that as cells multiplied and space became limited, those in the center experienced increased stress from surrounding cells. This stress caused them to significantly reduce their growth rate, creating bands of varying stress sensitivity that manifested as concentric circles.

The researchers developed both particle simulations for small-scale analysis and a continuum model to estimate behavior in larger cell populations. Both approaches yielded consistent results, confirming the robustness of their findings.

This discovery has potential implications for controlling harmful bacterial growth in infections or industrial settings. By identifying environmental factors that enhance cells' response to mechanical stress, it may be possible to slow exponential growth in unwanted microorganisms.

“I was definitely surprised to see that cells under this kind of mechanical stress can mitigate growth in that way,” Weady noted. “It’s interesting that they form these concentric circles where each ring shows how much they’ve been stifled by their neighbors, ultimately impacting how large they can grow. It’s a robust pattern that comes from a very simple rule, and it’s just something that no one had really thought to measure before.”

“I think the model is a useful tool for people who want to look at perturbations to the way cells respond, whether through stress, nutrient access or something else,” Weady said. “It’s very clear how to ask those questions with a model like this, so I find that exciting as far as what it will enable more broadly.”