Relay Architectures and Ecological Strategies of Quorum Sensing Effects on Microbial Interactions.

Microbial communities assemble in heterogeneous habitats, where quorum sensing (QS) influences interactions beyond signalling populations. Yet QS studies are commonly organized by signal type, circuit, or phenotype, obscuring the routes by which a QS event reaches neighbouring populations and why they prevail in particular settings. This Review synthesizes evidence from host-associated, terrestrial, marine, and aquatic systems to develop a two-dimensional framework for QS-mediated ecological effects. The framework distinguishes three relay architectures by which QS activity in one population affects another: direct perception of the source signal, exposure to a QS-regulated chemical effector, or response to a QS-associated change in a shared host or environment. It then identifies the ecological strategies that these architectures can support, including shared signal accessibility, reciprocal coordination, asymmetric cue responsiveness, resource monopolization, and competitive or community restructuring. Across habitats, spatial structure, resource accessibility, host-associated conditions, and temporal variability shape which relay architectures are feasible and the ecological consequences they generate. The framework positions QS as a context-dependent process through which population-state sensing is translated into neighbour responses, changes in habitat conditions, and community assembly. It establishes testable expectations for predicting which QS-mediated interactions arise in a habitat and for designing interventions that steer microbiome function.