Effects of Nanomaterials on Soil Microbial Communities, Plant-Rhizobia Symbiosis, and Mycorrhizal Colonization of Plant Roots in Biosolid-Amended Soil.

Engineered nanomaterials (ENMs) from consumer products are entering human waste streams and being discharged into agroecosystems in areas where biosolids are land-applied. ENMs are also increasingly being incorporated into nanopesticides and nanofertilizers. As a result of these applications, the potential exists for large amounts of ENMs to be introduced into agroecosystems. In addition to serving as prey species and in some cases promoting plant growth, soil bacteria and fungi participate in many important soil processes including nutrient cycling, organic matter decomposition and nitrogen fixation. Although studies have examined the effects of ENMs on pathogenic fungi and bacteria, few have examined the effects of soil accumulation of ENMs on beneficial bacteria and fungi. Here, a group of related recent studies that investigated the effects of ENMs on arbuscular mycorrhizal fungi (AMF), overall microbial community structure, and plant-rhizobia and plant-AMF symbioses in biosolids-amended soil are discussed. These studies utilized aged ENMs designed to simulate ultimate ENM transformation end-products that result from the processing of ENMs through wastewater treatment. Overall, ENM toxicity to the soil microbial community was dramatically reduced via simulated aging. However, in many cases, ENMs and aged ENMs induced different ecosystem responses from those observed in micron scale/ionic metal controls, suggesting that under certain circumstances, ENMs may present a risk distinct from micron scale/ionic metal materials.