Nitrogen fertilization management is required for soil phosphorus mobilization by phoD-harboring bacterial community assembly and pqqC-harboring bacterial 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, respectively) mediate P cycling. However, whether the microbial community assembly and keystone taxa of phoD- and pqqC-HB regulate P availability and distinct regulatory pathways between these two genes remain unclear. In this study, soil microbial community characteristics and P availability were investigated in four long-term (38-year) fertilization regimes: control with no fertilizer (CK), P fertilizer (PF), nitrogen (N) and P fertilizers (NP), and N fertilizer, P fertilizer, and manure (NPM). The N addition treatments (NP and NPM) significantly changed the community composition and increased the abundances of phoD- and pqqC-HB compared to the no-N addition treatments (CK and PF). Stochastic processes dominated the community assembly of both phoD- and pqqC-HB, and the relative contributions of stochasticity increased with N addition. Furthermore, the N addition treatments resulted in greater network complexity and higher abundances of keystone taxa of phoD- and pqqC-HB compared to those of the no-N addition treatments. 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 for phoD-HB, whereas keystone taxa contributed the most to labile Pi for 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.