From Single Strains to Synthetic Bacterial Communities: Microbial Remediation in Saline–A-Alkali Soil

Global salinization affects approximately one billion hectares of land in more than 100 countries, posing a severe threat to food security and ecosystem sustainability. Microbial remediation using plant growth-promoting microorganisms offers an eco-friendly alternative to physicochemical methods. However, bridging the gap between laboratory cultivation of single strains and field-scale application of synthetic microbial communities (SynComs) remains difficult, owing to inconsistent efficacy and a lack of unified design frameworks. This review examines the evolution from single strains to rationally designed SynComs for saline soil remediation. A ‘structure–function–mechanism’ framework is proposed, integrating five core microbial modules, namely ion regulation and osmotic stabilization, ethylene and phytohormone modulation, antioxidant activation, nutrient cycle activation, and systemic resistance induction. The review elucidates key determinants of synthetic community success, including functional complementarity, strain compatibility, and host–environment matching, while revealing a marked quantitative gap between controlled experiments and field performance. Key bottlenecks are identified, including the lack of high-throughput compatibility screening, poorly quantified long-term ecological risks, and the absence of standardized application guidelines across agro-ecological zones. Finally, emerging avenues are discussed, such as microbial–microalgal symbiosis and AI-assisted design, outlining a roadmap for next-generation smart microbial products integrated into climate-resilient farming systems.