This mini-review examines the role of rhizosphere microbiomes associated with cereal crops as functional models for extraterrestrial agriculture within closed ecological systems. The rhizosphere microbiome, conceptualized as a plant’s “second genome,” plays a central role in nutrient acquisition, stress resilience, and disease suppression through complex plant–microbe interactions. The review synthesizes current knowledge on microbiome assembly, emphasizing the contributions of soil-derived, seed-borne, and host genotype-dependent microbial communities. Particular attention is given to biological nitrogen fixation and other nutrient-mobilizing processes mediated by plant growth-promoting microorganisms, which are critical in environments where synthetic inputs are limited. Furthermore, the paper explores microbiome-mediated mechanisms of abiotic stress tolerance, including hormonal regulation and metabolic adaptation under extreme conditions. Advances in microbiome engineering - such as synthetic microbial consortia, host-mediated selection, and microbiome transplantation - are discussed as strategies to enhance plant productivity in controlled and resource-constrained environments, including space-based greenhouses. Finally, key translational challenges are identified, including context-dependent inoculant performance, ecological compatibility, and the gap between laboratory findings and field application. The review highlights the necessity of integrating multi-omics approaches, precision breeding, and genome editing technologies to fully exploit microbiome-assisted agriculture for sustainable extraterrestrial food production.
