Arbuscular Mycorrhizal Fungi Alleviate the Negative Effects of Iron Oxide Nanoparticles on Bacterial Community in Rhizospheric Soils

As a crucial reciprocal partner, arbuscular mycorrhizal fungi (AMF) can alleviate the negative effects of a variety of pollutants on their hosts and soil microbes. In our previous studies, such characteristics of AMF on plant growth were documented in response to metal engineered nanoparticle (ENP) treatments. However, the role of AMF in influencing ENP effects on soil microbes remains a matter of debate. To address this issue, we investigated the responses of soil microorganisms to iron oxide nanoparticles (Fe3O4NPs) along a concentration gradient (0.1, 1.0, and 10.0mg kg −1) in maize plants inoculated with and without AMF. The results showed that a high concentration of Fe3O4NPs significantly decreased the soil bacterial abundance and shifted the community composition, and these negative responses were associated with decreased soil dissolved organic C (DOC) contents in non-AMF-inoculated treatments. However, in AMF-inoculated treatments, no significant changes in soil biota or DOC contents were observed under Fe3O4NPs treatment. These results indicate that AMF alter the effects of Fe3O4NPs on soil microorganisms, possibly by influencing plant growth and organic matter released from plant roots, as DOC contents were impacted by AMF. Our findings suggest that AMF can influence Fe3O4NP-plant-microbe interactions; therefore, more attention should be focused on plant-associated microbes when evaluating the biological effects of nanoparticles.