Microbial activity in the rhizosphere can enhance root growth, improve nutrient bioavailability, and soil quality. However, it remains unclear how microbial populations form and establish along the root axis. This presentation will explore interactions taking place between root and bacteria when a root tip enters unexplored regions of soil. A dynamic model is proposed based on the couplings between root cell elongation, adhesion on root surfaces, carbon deposition, diffusion and decay, and chemotaxis. Results show root elongation rate, bacterial attachment and root cap carrying capacity are key traits for successful establishment, but we exclude chemotaxis as a tunable regulating factor because high chemotactic motility produces bacterial “booms” in the root elongation zone. This is the first time root growth kinematics is coupled to concepts of bacterial population dynamics, and using this approach we have derived general principles where bacterial attachment/detachment is a mechanism for both rhizosphere colonisation and subsequent dispersal of bacteria. This research will help understand the changing and steady-state structure and composition of rhizosphere microbial communities.

Thie is a joint work with Wendy K Silk (Department of Land, Air and Water Resources, University of California Davis, USA).