Dual Regulatory Role of Penicillium oxalicum SL2 in Soil: Phosphorus Solubilization and Pb Stabilization

Abstract

The mechanisms of the P. oxalicum SL2-mediated microbial community on phosphorus solubilization and Pb stabilization were investigated through a 90-day soil experiment. In the treatments inoculated with P. oxalicum SL2, the amount of P. oxalicum 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 P. oxalicum 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 P. oxalicum 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 Penicillium, Ascobolus, Humicola, and Spizellomyces in a fungal community increased the content of oxalate and AP, which directly decreased EDTA-Pb content, while the change of Bacillus, Ramlibacter, Gemmatimonas, and Candidatus Solibacter 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 P. oxalicum SL2 enhanced the microbial-induced phosphate precipitation process by activating soil microbial communities and regulating their ecological functions.

Forest-to-Cropland Conversion Reshapes Microbial Hierarchical Interactions and Degrades Ecosystem Multifunctionality at a National Scale

“…The finding that the cropland-declined microbial cluster drove the degradation of soil ecosystem multifunctionality (Figure b) made sense because the biodiversity of certain microbial clusters, rather than that of the overall microbial communities, were found to significantly correlate with ecosystem multifunctionality. − In the present study, the cropland-declined microbial cluster was positively associated with various ecological processes related with nutrient (e.g., carbon, nitrogen, phosphorus, and sulfur) cycles (Figure S11), probably because it contained a variety of taxa capable of improving soil nutrient status (Figures b and S11, and Table S5). Among the prokaryotes within the cropland-declined microbial cluster, the most abundant taxon Rhodoplanes genus was reported to be involved in nitrogen fixation; and Candidatus Solibacter genus was found to participate in the acquisition of carbon, nitrogen, and phosphorus from soils. − We further took Rhizobiales order that the Rhodoplanes genus belonged to as a typical microbial functional population participating in nitrogen fixation and found it indeed significantly and positively ( P = 0.001, R 2 = 0.15) correlated with the normalized abundance of nifH gene (encoding dinitrogenase reductase during nitrogen fixation, Table S2). Additionally, regarding the fungi within the cropland-declined microbial cluster, most of them were affiliated with Basidiomycota phylum, which are commonly regarded as major decomposers of dead organic matter and are thus indispensable in turning plant litter bioavailable in natural environments .…”