A contained laboratory physical model system was developed to investigate interactions between microorganisms isolated from the rhizosphere. Key physico-chemical characteristics of the plant root system were artificially recreated. In this way, their influence on microbial population dynamics could be studied in response to induced environmental change. The growth-limiting nutrient could be supplied to a population of bacteria, by radial diffusion from a central, cylindrical ultrafiltration membrane, in the place of a plant root. The diffusion rate of glucose across the ultrafiltration membrane was calculated, and the physical model system was tested in the presence of bacteria isolated from the rhizosphere. The study showed that a physical model could be used to make reasonable predictions about the behaviour of microorganisms in soil–root systems.