Characterization of a novel phosphate-solubilizing Paenibacillus sp. SN-8-1 with biofertilizer potential for soybean growth enhancement

Phosphorus (P) is the second most essential macronutrient required for plant growth, and its availability in most natural soils remains extremely low due to its predominance in insoluble forms. Moreover, phosphate-solubilizing microorganisms (PSMs) have gained increasing attention as sustainable and eco-friendly alternatives to conventional chemical fertilizers. However, the identification and characterization of novel PSM strains with enhanced phosphorus solubilization capabilities remains critical for advancing sustainable agricultural practices. Therefore, we isolated and taxonomically characterized a PSM, Paenibacillus sp. SN-8-1, through phylogenetic, physiological, and genomic analyses to evaluate its potential as a biofertilizer candidate. Average nucleotide identity (ANI) and DNA–DNA hybridization (DDH) values between SN-8-1 and other Paenibacillus species ranged from 68.3% to 81.6%, and 18.3% to 31.9%, which were much lower than the 95% and 70% of species-level threshold, indicating it was a novel strain. Whole-genome sequencing revealed that strain SN-8-1 possesses a comprehensive set of genes involved in phosphate solubilization (ipp, alp, epp), uptake (phnAB), transport (pstABCS, lat), and regulation (phoU, phoR, and phoB). The strain displayed a high capacity for phosphorus solubilization, which is predominantly driven by organic acid secretion, and assisted by phosphatase activity. Under controlled laboratory conditions, SN-8-1 produced substantial amounts of malic acid (707.13 mg/L), lactic acid (685.89 mg/L), and acetic acid (658.55 mg/L), contributing to acidification of the surrounding environment and enhanced P solubilization. Pot experiments further confirmed the functional potential of SN-8-1 in complex soil systems. Single inoculation significantly increased soybean height to 45.66 ± 0.47 cm, while shoot and root fresh biomass increased by 22.54% and 18.65%, respectively, compared with water-treated controls. Moreover, co-application of SN-8-1 with Ca₃(PO₄)₂ enhanced soil soluble phosphorus by 44.22%, demonstrating strong synergistic effects. Collectively, these results highlight Paenibacillus sp. nov. SN-8-1 as a promising biofertilizer candidate for improving soil phosphorus availability and advancing sustainable agricultural practices.