Enhancing maize phosphorus uptake through labile carbon-driven shifts in phoD- and bpp-harboring bacterial community in the hyphosphere of arbuscular mycorrhizal fungi

Background and Aims Hyphal exudates of arbuscular mycorrhizal (AM) fungi are key drivers mediating soil organic phosphorus (P) mineralization through the recruitment of functional bacteria in the hyphosphere. However, the specific functional bacteria related to soil organic P turnover in response to the major compounds present in hyphal exudates are not well understood, and the mechanisms by which these changes enhance organic P mineralization remain unclear. Methods In this study, we separately added three labile carbon (C) substrates (glucose, fructose, and citric acid) to the hyphosphere, and investigated the changes in bacterial communities harboring phoD and bpp genes, as well as the organic P mineralization response to the addition of these specific substrates. Results The addition of these labile carbon substrates significantly increased alkaline phosphatase activity in the hyphosphere, resulting in reduced available P concentrations, which consequently promoted maize growth and P uptake, particularly in the citric acid treatment. Compared to glucose and fructose, the addition of citric acid significantly altered the compositions of both phoD - and bpp -harboring bacterial communities, enriching the keystone P-solubilizing bacteria, including Gemmataceae, Pseudonocardiaceae, Xanthomonadaceae, Micrococcaceae, and Pseudomonadaceae. Co-occurrence network analysis revealed that interactions between phoD - and bpp -harboring bacterial taxa were more complex and stable in the citric acid treatment. Conclusion These results underscore that the labile C alters P-solubilizing bacterial communities and enhances organic P mineralization in the hyphosphere. This understanding provides strategies for manipulating the effective utilization of organic P through the interaction between AM fungi and P-solubilizing bacteria in the mycorrhizal pathway.