Nitrogen fertilization management is required for soil phosphorus mobilization by phoD community assembly and pqqC keystone taxa

phoD and pqqC gene occurrence in bacteria allows them to mobilize phosphorus (P) by mineralizing organic P (Po) and solubilizing inorganic P (Pi), respectively. Community characteristics of phoD- and pqqC-harboring bacteria (phoD- and pqqC-HB) mediate P cycling. However, whether the microbial community assembly and phoD- and pqqC-HB keystone taxa regulate P availability and the distinct regulatory pathways between these two genes remain unclear. Here, microbial community characteristics and soil P availability were investigated in four long-term fertilization regimes (38 years): no fertilizer (CK), P fertilizer (P), nitrogen (N) and P fertilizer (NP), and N and P fertilizer + manure (NPM). N addition treatments (NP and NPM) significantly changed the community composition and increased the abundance of phoD- and pqqC-HB compared to non-N addition treatments (CK and P). Stochastic processes dominated the community assembly for both phoD- and pqqC-HB, and the relative contributions of stochasticity increased with N addition. Furthermore, N addition treatments resulted in greater network complexity and higher keystone taxa abundance for phoD and pqqC genes compared to those of non-N addition treated soil. The keystone taxa implicated in P cycling were also associated with carbon (C) and N cycling processes. Microbial community composition and assembly processes were the main factors driving labile Pi in phoD-HB, whereas keystone taxa contributed the most to labile Pi in pqqC-HB. These results emphasize that distinct mechanisms of phoD- and pqqC-HB regulate P availability under fertilization management and underline the significance of microbial community assembly and keystone taxa in soil ecological functions, offering fresh perspectives on comprehending the biological processes facilitated by microorganisms in enhancing soil quality.