摘要 : Microbial community composition differs between soil aggregate sizes, which markedly affects phosphorus cycling in agroecosystems. The genes phoD and pqqC regulate phosphorus mobilization and act as molecular markers of phosphate-... 展开 Microbial community composition differs between soil aggregate sizes, which markedly affects phosphorus cycling in agroecosystems. The genes phoD and pqqC regulate phosphorus mobilization and act as molecular markers of phosphate-mobilizing bacteria, but differences in phoD- and pqqC-harbouring bacterial communities between different-sized aggregates remain unclear. The abundance and community composition of phoD- and pqqC-harbouring bacteria were determined in three aggregate size classes (> 250, 63-250, and < 63 mu m) in calcareous soil from northwest China in a 38-year experiment. The > 250 and < 63 mu m aggregates showed the lowest and highest cumulative relative abundance, respectively, of operational taxonomic units in phoD- and pqqC-harbouring bacterial communities. Simpler co-occurrence networks (fewer nodes, links, and shorter network diameter) were found in > 250 and < 63 mu m aggregates, compared to 63-250 mu m aggregates. For phoD and pqqC gene networks, > 250 and < 63 mu m aggregates (phoD: alpha-Proteobacteria and Actinomycetia; pqqC: Actinomycetia) contained keystone taxa distinct from 63 to 250 mu m aggregates (phoD: Rubrobacteria and gamma-Proteobacteria; pqqC: beta-Proteobacteria). Total nitrogen (TN) and Olsen-P significantly affected the abundance and community richness of phoD- and pqqC-harbouring bacteria. phoD and pqqC gene abundance was determined by TN in > 250 mu m aggregates, whereas they were indirectly determined by Olsen-P in < 63 mu m aggregates. Our results emphasized the distinct distribution characteristics of phosphate-mobilizing bacterial communities in different-sized aggregates and identified the main factors regulating phoD and pqqC gene abundance. 收起