Dual Regulatory Role of <i>Penicillium oxalicum</i> SL2 in Soil: Phosphorus Solubilization and Pb Stabilization

Abstract

The mechanisms of the <i>P. oxalicum</i> SL2-mediated microbial community on phosphorus solubilization and Pb stabilization were investigated through a 90-day soil experiment. In the treatments inoculated with <i>P. oxalicum</i> SL2, the amount of <i>P. oxalicum</i> SL2-GFP remained at 77.8%-138.6% of the initial inoculation amount after 90 days, and the available phosphorus (AP) content increased 21.7%-40.8% while EDTA-Pb decreased 29.9%-43.2% compared with CK treatment. SEM-EDS results showed that <i>P. oxalicum</i> SL2 changed the agglomeration degree of microaggregates and promoted the combination of Pb with C and O elements. These phenomena were enhanced when applied with Ca₃(PO₄)₂. Microbial community analysis showed that <i>P. oxalicum</i> SL2 improved soil microbial activity, in which the fungi absolute abundance increased about 15 times within 90 days. Correlation analyses and a partial least-squares path model showed that the activation of <i>Penicillium</i>, <i>Ascobolus</i>, <i>Humicola</i>, and <i>Spizellomyces</i> in a fungal community increased the content of oxalate and AP, which directly decreased EDTA-Pb content, while the change of <i>Bacillus</i>, <i>Ramlibacter</i>, <i>Gemmatimonas</i>, and <i>Candidatus Solibacter</i> in the bacterial community regulated Fe/Mn/S/N cycle-related functions, thus promoting the conversion of Pb to oxidizable state. Our findings highlight that <i>P. oxalicum</i> SL2 enhanced the microbial-induced phosphate precipitation process by activating soil microbial communities and regulating their ecological functions.