Abstract
Phosphorus (P), one of the three primary macronutrients essential for plant growth, predominantly exists in soil as unavailable forms for plant uptake. Rhizosphere bacteria can mobilize the unavailable P through two key processes: organic phosphorus mineralization and inorganic phosphorus solubilization. Despite their ecological significance, the diversity and community structure of P-mobilizing bacteria in plant rhizospheres remain insufficiently characterized. In this study, we employed culturomics to isolate bacteria from tobacco rhizosphere and systematically evaluated their P mobilization activities. The P mobilization mechanism was analyzed through whole genome sequence analyses, and the promotion effect was evaluated by greenhouse experiment. A total of 266 P mobilization bacteria were screened, representing 41.50 % of the total isolates. These bacteria were further classified as 49 genera in four phyla: Pseudomonadota (63.16 %), Bacillota (18.80 %), Bacteroidota (10.15 %), and Actinomycetota (7.89 %), with Pseudomonas (25.10 %) and Bacillus (16.47 %) as dominant genera (>10 %). The collection comprised 232 P-mineralization bacteria (PMB) (47 genera), 126 P-solubilizing bacteria (PSB) (33 genera), and 92 dual-functional (26 genera) strains. PMB strains exhibited higher α-diversity and greater numerical abundance across all sampling sites than PSB. Genomic analyses revealed that Pseudomonadota strains displayed exceptional genetic flexibility, harboring more P mobilization genes than other phyla strains. Greenhouse experiments demonstrated that PSB strains significantly enhanced tobacco seedling growth, including shoot and root biomass, stem diameter and leaf area, increased both plant P content and rhizosphere soil available P concentrations. Our study provides new insights into microbial-mediated mechanisms governing phosphorus mobilization and biogeochemical cycling within plant rhizosphere ecosystems.