Bacterial chemotaxis to a finite localized source

Chemotaxis, the ability to sense and respond to chemical gradients, enables microorganisms to forage for food, colonize new environments, and locate hosts and symbionts. This phenomenon occurs across various length scales, environments, and cell concentrations, from oceans to the human body. Previous research has examined factors like environmental porosity, fluid flow, and cell concentration, often focusing on dense bacterial populations responding to abundant, global attractant sources. However, the response to patchy attractant sources remains less understood. In this study, we conduct experiments and simulations to investigate bacterial chemotaxis in a porous environment with a local, ephemeral attractant source. We find that cell density and attractant size influence whether bacteria accumulate or form chemotactic bands. These findings enhance our understanding of chemotaxis in real-world scenarios and offer valuable tools for engineering bacterial suspensions in bioremediation applications.