Plant growth-promoting bacteria reshape rhizosphere microbial networks and biochemical properties to drive sustainable Zea mays growth

Plant growth-promoting bacteria (PGPB) inoculants are crucial for sustainable agriculture, enhancing ecological balance and crop yields. Soil microbial communities are integral to maintaining soil fertility and ecological stability. However, the precise impacts of exogenous PGPB inoculants on the intricate relationships within rhizosphere microbial communities remain underexplored under phosphorus (P)-deficiency conditions. This study investigated the relationships between laboratory-screened endophytic and rhizosphere PGPB and microbial communities in a Zea mays pot experiment, assessing their effects on soil biochemical properties and plant physiological parameters. Results revealed that PGPB inoculation significantly influenced the relative abundance of rhizosphere microbial communities, enhancing the modularity of indigenous bacterial and differential microbiota. Notably, highly connected nodes within microbial community modules suggested enhanced functional interactions. Kruskal-Wallis rank-sum tests for intergroup differences, network analysis of differential microbiota, and PICRUSt2 functional prediction demonstrated that exogenous PGPB inoculants significantly increased the relative abundance of microbiota associated with carbon and nitrogen metabolism, including Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium sp., Ciceribacter sp., and Azospirillum sp. Further analysis using db-RDA, correlation network maps, and partial least squares structural equation modeling revealed the close relationships between these microbial communities and key soil nutrient factors (e.g., soil organic matter, available phosphorus), soil enzyme activities (e.g., acid phosphatase, alkaline phosphatase, urease, cellulase), and plant physiological indicators (e.g., photosynthetic rate, soluble sugar, and soluble protein content). Our study demonstrates that PGPB inoculation enhances beneficial bacteria, microbial interactions, and rhizosphere soil properties, supporting Z. mays growth and development under P-deficiency conditions. These findings improve our understanding of PGPB's ecological roles and growth-promoting mechanisms, encouraging their broader use in sustainable agriculture.