Functional and genomic characterization of phosphorus-solubilizing enhancement through Aliirhizobium wenxiniae SN-4-17.

INTRODUCTION: Phosphorus (P) availability is a major limiting factor in crop productivity due to the predominance of insoluble phosphate complexes in soil. METHODS: A phosphate-solubilizing bacterium, Aliirhizobium wenxiniae SN-4-17, was isolated from soybean rhizosphere soil and functionally characterized using physiological, genomic, and biochemical approaches. RESULTS: Strain SN-4-17 exhibited strong phosphorus-solubilizing activity, releasing up to 652.9 mg/L soluble P at pH 4.0 in vitro. Genome analysis (6.41 Mb) revealed genes associated with phosphorus metabolism, including phosphate transport systems, alkaline phosphatases, and CP lyase pathways. Organic acid profiling by HPLC revealed the production of acetic acid, oxalate, and succinic acid as the dominant metabolites, suggesting that organic acid secretion is the primary mechanism responsible for phosphate solubilization. The highest soluble P concentration was observed at pH 4.0 and 30 °C; however, the elevated P solubilization under strongly acidic conditions may have been partly attributable to abiotic dissolution of Ca₃(PO₄)₂. Although no significant effects on plant biomass were observed, the co-application of SN-4-17 with Ca₃(PO₄)₂ in pot experiments resulted in a 106% increase in soil available phosphorus compared to the control. CONCLUSION: These findings demonstrate that A. wenxiniae SN-4-17 is an efficient phosphate-solubilizing bacterium with potential application to enhance phosphorus availability in agricultural systems.