Engineered nanomaterials and symbiotic dinitrogen fixation in legumes

Molecular Mechanisms of Nanomaterial-Bacterial Interactions Revealed by Omics—The Role of Nanomaterial Effect Level

“…To gain a better understanding of how ENM effects may change over time and at different doses, future test designs should include wider coverage of these test parameters and also consider the aspect of heterogeneity of the bacterial population upon ENM exposures. Omics approaches have a potential to greatly advance the mechanistic understanding of bacterial-ENM interactions, which is needed, especially in light of the development of nanomedicine and the recently recognized importance of the microbiome in human health ( Zhang et al, 2020 ), and an increasing need for sustainable agriculture where plant-symbiotic microorganisms and nano-enabled agrochemicals play important roles ( Holden et al, 2018 ).…”

Physical Properties of Carbon Nanomaterials and Nanoceria Affect Pathways Important to the Nodulation Competitiveness of the Symbiotic N2‐Fixing Bacterium Bradyrhizobium diazoefficiens

“…[6] However, the effects of emerging environmental pollutants such as engineered nanomaterials (ENMs) on symbiotic N 2 fixation are poorly understood. [7] Scenarios by which ENMs may enter soils and affect crop plants involve either intentional (e.g., application of nanofertilizers or nanopesticides) [8] or incidental exposures. [9] Incidental exposure may occur through applying biosolids as fertilizers from wastewater treatment plants, [10] using untreated sewage for irrigating crops, [11] or atmospheric deposition of airborne ENMs.…”

Soybeans Grown with Carbonaceous Nanomaterials Maintain Nitrogen Stoichiometry by Assimilating Soil Nitrogen to Offset Impaired Dinitrogen Fixation

“…Engineered nanomaterials (ENMs) with many exceptional properties are increasingly incorporated into commercial products , and released into waste streams . When disposing ENM-containing wastewater treatment plant biosolids or sewage on agricultural lands, ENMs can enter soils inadvertently. − ENMs may also be directly applied to soils as agrochemicals ( e . g ., pesticides and fertilizers). , Although nanotechnology offers great promise in enhancing food security, the risks associated with nanotechnology in agriculture are still not well understood, , including the potential effects of ENMs on the important ecosystem service of dinitrogen (N 2 ) fixation in legumes …”

“…Besides being agronomically and economically important food, animal feed, and biomass plants themselves, legumes are grown in rotation, intercropped, or as cover-crops to improve soil fertility. − This is because legumes can form symbioses with N 2 -fixing bacteria in root nodules, where atmospheric N 2 is converted into ammonia in situ by bacteroid nitrogenase using plant photosynthate as the reductant. , Through N 2 fixation, legume crops supply 21 Tg of bioavailable N annually into agroecosystems, thereby partly offsetting the need for synthetic fertilizer . For example, in the U.S., the average amount of N fertilizer per acre used for soybean, the most widely grown legume crop, is less than 4% of that used in corn agriculture. , Thus, legume N 2 fixation can mitigate the energy consumption, greenhouse gas emissions, water contamination, and biodiversity loss associated with fertilizer production and application. − However, legume N 2 fixation is a complex process (involving N 2 -fixing bacterial infection of roots, nodule formation and function) that is vulnerable to environmental perturbations, − such as ENMs in soils …”

“…When exposed to ENMs, legume N 2 -fixing symbioses can be compromised, resulting in decreased nodule number and size, bacteroid density, and N 2 fixation potential ( i . e ., the specific activity of nitrogenase). − However, these prior studies did not address the time-integrated, whole-plant N 2 fixation rate nor the amount of plant N that may be derived from other sources ( e .…”