Engineering rhizobacterial communities for soil and plant health.

Rhizobacteria play a central role in supporting plant growth, contributing to nutrient acquisition, stress tolerance and disease suppression. Harnessing and improving rhizosphere microbial communities therefore represents a promising avenue towards more sustainable agriculture. Recent advances in microbiome ecology and synthetic biology have enabled the rational design of microbial consortia. Synthetic communities are widely used as tractable models to study ecological interactions and are increasingly explored as biofertilizers and biocontrol agents. Here, we define engineered microbial communities (EngComs) as microbial consortia augmented with strains carrying synthetic genetic circuits. These systems extend SynCom approaches by enabling programmable functions, such as intercellular communication, division of labour, biosensing and controlled nutrient mobilization, ultimately improving functional stability in complex environments. Beyond bacteria-bacteria interactions, we highlight emerging strategies to engineer plant-microbe interfaces through synthetic signalling pathways and multi-input genetic circuits that enable context-dependent responses. Despite this progress, the engineering of rhizobacteria for real soil environments remains at an early stage. Most systems are still characterized in simplified or artificial conditions, and key challenges persist, including environmental complexity, genetic stability, biocontainment and regulatory constraints. Addressing these limitations will be essential to translate engineered functions from laboratory settings to the field. Overall, continued integration of synthetic biology with ecological and biophysical understanding of the rhizosphere will pave the way for programmable plant-microbe systems, offering new opportunities to enhance crop productivity while reducing environmental impact.