Quorum sensing (QS) is a mechanism which enables many bacterial species to coordinate their behaviour via release and uptake of signalling molecules (called autoinducers, AI). In the underlying gene regulatory system, typically a positive feedback loop for the AI production is included. AI regulate a variaty of processes like bioluminescence or virulence factors. But some of the regulated processes may lead to a negative feedback on the QS system. We consider two examples from the soil bacterium Pseudomonas putida: the production of an AI-degrading enzyme, and the initialisation of bacterial detachment (i.e., they start to leave their usual attached microcolonies). Corresponding ODE/DDE and PDE models allow to analyse possible temporal and spatial consequences (e.g. leading to bifurcations) and to discuss the benefit thereof for the bacterial population as a whole.

Gene regulatory system; positive feedback; negative feedback; bifurcations; bacteria; quorum sensing