Arbuscular mycorrhizal fungus differentially regulates P mobilizing bacterial community and abundance in rhizosphere and hyphosphere

Arbuscular mycorrhizal fungi (AMF) promote the P uptake of host plants not only by themselves but also by regulating P mobilizing bacterial (PMB) community in the plant-AMF-PMB holobiont. However, the differences in PMB community between two important niches (rhizosphere vs. hyphosphere) as regulated by AMF are scarcely revealed. With stylo (Stylosanthes guianensis) and bahiagrass (Paspalum notatum) inoculated with AMF Rhizophagus irregularis DAOM 197198 in compartmented rhizoboxes, the objective of this study was to compare PMB community, phosphatase activity and P status in rhizosphere and hyphosphere. The abundances of PMB functional genes (phoD, phoC, gcd, pqqC) were also quantified. Mycorrhizal inoculation greatly increased plant biomass, and enhanced the phosphatase activity in both the rhizosphere and the hyphosphere. The abundances of phoC and pqqC in the rhizosphere were significantly increased by AMF, but those in the hyphosphere were not affected. Sequencing of phoD and pqqC indicated that PMB community in the rhizosphere differed very much from that in the hyphosphere. AMF greatly altered PMB community structure in both the rhizosphere and the hyphosphere, and enriched different PMB taxa in these two niches. Taken together, these data reveal that AMF regulate PMB community in the rhizosphere more greatly than that in the hyphosphere and PMB are mainly shaped by roots rather than AMF in this study. Our results highlight the importance of regulating and utilizing the PMB community not only in the rhizosphere but also in the hyphosphere.