CuO Nanoparticles Alter the Rhizospheric Bacterial Community and Local Nitrogen Cycling for Wheat Grown in a Calcareous Soil

Abstract

The application of nanoparticles (NPs) to soils, as either fertilizers or fungicides (e.g., CuO NPs), has been proposed to improve the sustainability of agriculture. The observed effects could result directly from the NP−plant interactions or indirectly through effects on the soil microbiome. The objective of this study was to assess the effects of CuO NPs on the changes in the bacterial community structure and nitrogen-cycling-associated functions in a high pH soil and to correlate these changes with nitrate accumulation, soil parameter changes, and plant growth over 28 days. Triticum aestivum seedlings were exposed to 50 mg/kg CuO NPs, 50 mg/kg CuSO 4 , or 0.5 mg/kg CuSO 4 in a standard soil (Lufa 2.1 soil, pH adjusted to 7.6). While Cu treatments reduced nitrate accumulation in the bulk soil, the effects were opposite in the rhizosphere (the soil influenced by root exudates). While nitrate accumulation in bulk soil negatively correlated with total Cu concentration, part of the nitrate concentration in the rhizosphere was explained by root uptake during plant growth, the rest being modulated by Cu treatments. The abundance of genes involved in the nitrogen cycle in the rhizosphere soil correlated with the ionic copper concentration. The increased nitrate concentration in the rhizosphere correlated with an increase of the gene abundance related to the nitrogen fixation and a decrease of denitrification gene abundance. Microbial diversity in bulk or rhizosphere soil under the different treatments alone could not explain these variations, while differences in the assemblages of bacteria associated with these functional gene abundances gave good insights. This study highlights the complexity of microbial Nrelated function in the rhizosphere and the need to characterize the rhizosphere soil, plant growth and root activity, NP (bio)transformations, along with microbial networks, to understand the impact of agrochemicals (here CuO NPs) on soil fertility.

Microbial response to copper oxide nanoparticles in soils is controlled by land use rather than copper fate

“…Most do not include Cu adsorbed to phyllosilicate minerals commonly found in soils from arid or Mediterranean climates or those that have undergone little pedogenisis. 27,33,103,[108][109][110][111][112][113][114][115][116] Rather, Cu from CuO nanoparticles is often modeled as complexed by SOM, neoformed as Cu x S, or adsorbed by iron or aluminum oxides. 27,33,109,116 However, reducing conditions such as those that lead to Cu x S formation are less likely to occur in soils from arid or Mediterranean climates.…”

“…27,33,103,[108][109][110][111][112][113][114][115][116] Rather, Cu from CuO nanoparticles is often modeled as complexed by SOM, neoformed as Cu x S, or adsorbed by iron or aluminum oxides. 27,33,109,116 However, reducing conditions such as those that lead to Cu x S formation are less likely to occur in soils from arid or Mediterranean climates. 107,113 Further, soils in these climates, and more generally, soils that have undergone minimal mineral weathering, are dominated by phyllosilicate minerals and are unlikely to contain significant amounts of iron or aluminum oxides.…”

Catalyzing Holistic Agriculture Innovation Through Industrial Biotechnology

“…256,265,266 Agronomic practices such as tillage, chemicals application for weed and pest controls, row spacing, and the use of cover crops also influence rhizosphere and phyllosphere microbiomes by altering the physical and chemical structure of the environment or directly targeting members of the microbial communities. [267][268][269][270][271] The many opportunities that exist for intervening in plant metaphenomic systems underscore the challenges we face in trying to take a holistic approach to developing microbial solutions for agriculture. It is clear such an effort must be multidisciplinary in nature.…”

Metabolomic and bioenergetic responses of human hepatocellular carcinoma cells following exposure to commercial copper hydroxide nanopesticide

“…Trophic transfer has been reported for several nanoparticles in aquatic and terrestrial food chains. [15][16][17][18][19][20][21][22] Based on the limited studies available, Cu(OH) 2 nanopesticide exposure can adversely affect aquatic organisms, including the estuarine amphipod Leptocheirus plumulosus, 23 embryonic zebrafish (Danio rerio), 24,25 microbial communities, [26][27][28][29] and other non-target organisms. Most significant is that there are no data on the potential for copper nanopesticide-induced toxicity in mammals, especially humans.…”