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1. Copper oxide nanoparticle dissolution at alkaline pH is controlled by dissolved organic matter: influence of soil-derived organic matter, wheat, bacteria, and nanoparticle coating

   https://doi.org/10.1039/d0en00574f  

   Hortin, J. M.; Anderson, A. J.; Britt, D. W.; Jacobson, A. R.; McLean, J. E. (January 2020, Environmental Science: Nano)

   Dissolution of CuO nanoparticles, releasing Cu ions, is a primary mechanism of Cu interaction in the rooting zone of plants. CuO dissolution is sometimes incorrectly considered negligible at high pH, since complexation of Cu with dissolved organic matter may enhance nanoparticle dissolution. Therefore data on the effects of plant-microbial-soil interactions on nanoparticle dissolution, particularly in alkaline soils, are needed. Dissolution of CuO nanoparticles (100 mg kg −1 Cu) was studied in sand supplemented with factorial combinations of wheat growth, a root-colonizing bacterium, and saturated paste extracts (SPEs) from three alkaline, calcareous soils. In control sand systems with 3.34 mM Ca(NO 3 ) 2 solution, dissolved Cu was low (266 μg L −1 Cu). Addition of dissolved organic matter via wheat root metabolites and/or soil SPEs increased dissolved Cu to 795–6250 μg L −1 Cu. Dissolution was correlated with dissolved organic carbon ( R = 0.916, p < 0.0001). Ligands >3 kDa, presumably fulvic acid from the SPEs, complexed Cu driving solubility; the addition of plant exudates further increased solubility 1.5–3.5×. The root-colonizing bacterium decreased dissolved Cu in sand pore waters from planted systems due to metabolism of root exudates. Batch solubility studies (10 mg L −1 Cu) with the soil SPEs and defined solutions containing bicarbonate or fulvic acid confirmed elevated CuO nanoparticle solubility at >7.5 pH. Nanoparticle dissolution was suppressed in batch experiments compared to sand, via nanoparticle organic matter coating or homoconjugation of dissolved organic matter. Alterations of CuO nanoparticles by soil organic matter, plant exudates, and bacteria will affect dissolution and bioavailability of the CuO nanoparticles in alkaline soils. 

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2. Soil-derived fulvic acid and root exudates, modified by soil bacteria, alter CuO nanoparticle-induced root stunting of wheat via Cu complexation

   https://doi.org/10.1039/c9en00728h  

   Hortin, J. M.; Anderson, A. J.; Britt, D. W.; Jacobson, A. R.; McLean, J. E. (December 2019, Environmental Science: Nano)

   CuO nanoparticles (NPs) are explored as fungicides and fertilizers, and are increasingly likely to be applied to agricultural soils. Consequently, interactions of CuO NPs with soil pore water (SPW) components, plants, and microbes must be understood. These experiments examined whether dissolved natural organic matter (DNOM) from SPW, or root/bacterial exudates, changed wheat ( Triticum aestivum L. v. Deloris) responses to 100 mg kg −1 (Cu/sand) as CuO NPs. Seedlings were grown in sand with 3.34 mM Ca(NO 3 ) 2 or one of three SPWs, differing in DNOM concentration and composition. At 10 days post-germination, CuO NPs stunted roots by 59% in the 3.34 mM Ca(NO 3 ) 2 and 26–35% in the three SPWs compared to plants grown without NPs. Malate, citrate, gluconate, and 2′-deoxymugineic acid (DMA), were elevated 1.3 to 5-fold in the rhizosphere with CuO NPs present. Cu was bioavailable through metallo-organic complexes, including Cu–DMA and Cu–gluconate. Fulvic acid in SPWs mitigated CuO NP-induced wheat root shortening. Pseudomonas chlororaphis O6 eliminated malate and citrate in the rhizospheres, reduced rhizosphere dissolved Cu ∼18–66%, and reduced root Cu 39% across all SPWs while enhancing root stunting ∼17% more across all SPWs than non-inoculated wheat grown with CuO NPs. Thus, both SPW components and root microbial colonization influenced wheat responses to CuO NPs. These interactions are likely in agricultural soils with additional processes, such as ion sorption, to influence CuO NP phytotoxicity, highlighting the importance of considering not just the target plant, but soil properties and associated microbiomes when evaluating impacts of NPs in agricultural usage. 

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3. Advanced material modulation of nutritional and phytohormone status alleviates damage from soybean sudden death syndrome

   https://doi.org/10.1038/s41565-020-00776-1  

   Ma, Chuanxin; Borgatta, Jaya; Hudson, Blake Geoffrey; Tamijani, Ali Abbaspour; De La Torre-Roche, Roberto; Zuverza-Mena, Nubia; Shen, Yu; Elmer, Wade; Xing, Baoshan; Mason, Sara Elizabeth; et al (October 2020, Nature nanotechnology)

   Customized Cu3(PO4)2 and CuO nanosheets and commercial CuO nanoparticles were investigated for micronutrient delivery and suppression of soybean sudden death syndrome. An ab initio thermodynamics approach modelled how material morphology and matrix effects control the nutrient release. Infection reduced the biomass and photosynthesis by 70.3 and 60%, respectively; the foliar application of nanoscale Cu reversed this damage. Disease-induced changes in the antioxidant enzyme activity and fatty acid profile were also alleviated by Cu amendment. The transcription of two dozen defence- and health-related genes correlates a nanoscale Cu-enhanced innate disease response to reduced pathogenicity and increased growth. Cu-based nanosheets exhibited a greater disease suppression than that of CuO nanoparticles due to a greater leaf surface affinity and Cu dissolution, as determined computationally and experimentally. The findings highlight the importance and tunability of nanomaterial properties, such as morphology, composition and dissolution. The early seedling foliar application of nanoscale Cu to modulate nutrition and enhance immunity offers a great potential for sustainable agriculture. 

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4. Plasma Metabolomics in a Nonhuman Primate Model of Abdominal Radiation Exposure

   https://doi.org/10.3390/metabo11080540  

   Jun, Se-Ran; Boerma, Marjan; Udaondo, Zulema; Richardson, Sasha; Thrall, Karla D.; Miousse, Isabelle R.; Seng, John; Pathak, Rupak; Hauer-Jensen, Martin (August 2021, Metabolites)

   The acute radiation syndrome is defined in large part by radiation injury in the hematopoietic and gastrointestinal (GI) systems. To identify new pathways involved in radiation-induced GI injury, this study assessed dose- and time-dependent changes in plasma metabolites in a nonhuman primate model of whole abdominal irradiation. Male and female adult Rhesus monkeys were exposed to 6 MV photons to the abdomen at doses ranging between 8 and 14 Gy. At time points from 1 to 60 days after irradiation, plasma samples were collected and subjected to untargeted metabolomics. With the limited sample size of females, different discovery times after irradiation between males and females were observed in metabolomics pattern. Detailed analyses are restricted to only males for the discovery power. Radiation caused an increase in fatty acid oxidation and circulating levels of corticosteroids which may be an indication of physiological stress, and amino acids, indicative of a cellular repair response. The largest changes were observed at days 9 and 10 post-irradiation, with most returning to baseline at day 30. In addition, dysregulated metabolites involved in amino acid pathways, which might indicate changes in the microbiome, were detected. In conclusion, abdominal irradiation in a nonhuman primate model caused a plasma metabolome profile indicative of GI injury. These results point to pathways that may be targeted for intervention or used as early indicators of GI radiation injury. Moreover, our results suggest that effects are sex-specific and that interventions may need to be tailored accordingly. 

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5. Metabolomic Responses of Green Alga Chlamydomonas reinhardtii Exposed to Sublethal Concentrations of Inorganic and Methylmercury.

   https://doi.org/10.1021/ acs.est.0c08416  

   Slaveykova, Vera I.; Majumdar, Sanghamitra; Regier, Nicole; Li, Weiwei; Keller, Arturo A. (February 2021, Environmental science and technology)

   Metabolomics characterizes low-molecular-weight molecules involved in different biochemical reactions and provides an integrated assessment of the physiological state of an organism. By using liquid chromatography–mass spectrometry targeted metabolomics, we examined the response of green alga Chlamydomonas reinhardtii to sublethal concentrations of inorganic mercury (IHg) and monomethylmercury (MeHg). We quantified the changes in the levels of 93 metabolites preselected based on the disturbed metabolic pathways obtained in a previous transcriptomics study. Metabolites are downstream products of the gene transcription; hence, metabolite quantification provided information about the biochemical status of the algal cells exposed to Hg compounds. The results showed that the alga adjusts its metabolism during 2 h exposure to 5 × 10–9 and 5 × 10–8 mol L–1 IHg and MeHg by increasing the level of various metabolites involved in amino acid and nucleotide metabolism, photorespiration, and tricarboxylic acid (TCA) cycle, as well as the metabolism of fatty acids, carbohydrates, and antioxidants. Most of the metabolic perturbations in the alga were common for IHg and MeHg treatments. However, the exposure to IHg resulted in more pronounced perturbations in the fatty acid and TCA metabolism as compared with the exposure to MeHg. The observed metabolic perturbations were generally consistent with our previously published transcriptomics results for C. reinhardtii exposed to the comparable level of IHg and MeHg. The results highlight the potential of metabolomics for toxicity evaluation, especially to detect effects at an early stage of exposure prior to their physiological appearance. 

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