Pristine and Sulfidized Zinc Oxide Nanoparticles Promote the Release and Decomposition of Organic Carbon in the Legume Rhizosphere

Methanogenic response of paddy soils exposed to zinc oxide nanoparticles and sulfurized products

The use of zinc oxide nanoparticles (ZnO NPs) in agriculture is expanding, yet their effects on microbial ecology in flooded paddy soils remain unclear. This study examined the influence of ZnO NPs and their sulfide derivatives (S-ZnO NPs) on methane production in paddy soils. Results showed that ZnO NPs at a concentration of 1000 mg/kg significantly inhibited methane production by 28.97 % in an acid soil and by 26.83 % in an alkaline soil. S-ZnO NPs at the same concentration did not significantly affect methane production in the alkaline soil and increased it by 15.33 % in the acid soil. High-throughput sequencing revealed that ZnO NPs significantly altered the microbial community structure, affecting the prevalence of methanogenic organisms like Methanosarcina in the acid soil and Methanobacterium in the alkaline soil. Quantitative PCR analysis showed a reduction in the expression of methanogenic gene (mcrA) and total bacterial 16S rRNA genes with ZnO NPs exposure, but S-ZnO NPs had a lesser impact on these genes. This research highlights the more toxic impact of ZnO NPs compared to S-ZnO NPs on methane production and microbial communities in paddy soils, emphasizing the necessity for careful evaluation of nanoparticles in agricultural use to avoid ecological disturbances.

Strategy for enhanced soil lead passivation and mitigating lead toxicity to plants by biochar-based microbial agents

In the study, bone char (BC) backed biochemical composite coupling with phosphate-solubilizing bacteria (CFB1-P) was prepared to explore the passivation performance of lead (Pb) in soil and the mitigation effect on plant growth under Pb stress by measuring change of soil Pb speciation, plant growth parameters and physiological and biochemical indexes. After 30 d of remediation, addition of 1 % CFB1-P could effectively reduce 55.43 % of Pb labile fractions and converted them into Fe-Mn oxide and residual forms. Meanwhile, the bioavailability of Pb was not significantly affected by wetting-drying and freezing-thawing after 20 times cycles (the DTPA-Pb content only increased 6.91-7.35 mg/kg), which proved that the CFB1-P had an excellent prospect of passivating Pb. Moreover, the CFB1-P effectively increased soil fertility and improved soil enzyme activity. The application of CFB1-P could reshape the soil microbial community by recruiting beneficial microorganisms (Bacillus, Sulfurifustis, and Gaiella), which contributed to the improvement of Pb-contaminated soil quality. Furthermore, the fresh weight, photosynthetic pigment concentration, stems and roots length of cucumber seedings were significantly increased. Pb in the cucumber seedings and antioxidant enzyme activities of cucumber seedings were prominently decreased. Therefore, the study can offer a preferable comprehending for the advance of sustainable high-efficiency materials which microbial agent based on functional biochar remediated Pb-polluted soil.

Functionalized Silica Nanoparticles Mitigate Salt Stress in Soybean: Comprehensive Insights of Physiological, Metabolomic, and Microbiome Responses

Silica nanoparticles (SiO2 NPs) have potential for mitigating salt stress in crops; however, the effects of surface modifications in enhancing their effectiveness remain unclear. This study investigated the effects of pristine and functionalized SiO2 NPs (SiO2-NH2 and SiO2-COOH) on soybean growth, root metabolism, and microbiome dynamics under 200 mM NaCl stress. All SiO2 NPs treatments significantly reduced Na+/K+, with SiO2-COOH NPs showing the greatest efficacy, reducing by 46.6%. Enhanced salt tolerance correlated with altered root metabolism, including increased l-tyrosine, uridine, and indole-3-acetamide levels and enrichment of stress-response pathways. Furthermore, SiO2-COOH NPs enhanced microbial diversity, increasing the abundance of beneficial genera Variovorax and Pseudomonas in the endosphere, and Haliangium and Arthrobacter in the rhizosphere. Microbe-metabolite correlations suggest that altered root exudation under functionalized SiO2 NPs treatments selectively recruits beneficial bacteria, enhancing salt tolerance. These findings highlight the potential of functionalized SiO2 NPs, particularly SiO2-COOH, as nanoenabled biostimulants for sustainable agriculture.

Absorption and transport of different ZnO nanoparticles sizes in Agrostis stolonifera: Impacts on physiological, biochemical responses, root exudation, and microbial community structure

Nanomaterials play a crucial role in various applications, but their environmental impact necessitates effective recycling strategies. This study investigates the effects of different ZnO nanoparticles (ZnO-NPs) sizes (0, 30, 50, and 90 nm) on Agrostis stolonifera, focusing on physiological and biochemical responses, root exudate, and microbial community structure. The results showed that the most optimal physiological and biochemical responses, including enhanced plant growth and increased activities of superoxide dismutase, peroxidase, and catalase, were observed at 50 nm ZnO-NPs. Agrostis stolonifera accumulated more ZnO-NPs at 30 nm, with Zn content in root and leaf tissues reaching 186 mg/kg and 294 mg/kg, respectively. Meanwhile, SEM-Mapping and TEM analyses confirmed the absorption and transport of ZnO-NPs within Agrostis stolonifera. Furthermore, root exudates analysis revealed an increase in the types of organic matter secreted by roots at 30 nm and 50 nm ZnO-NPs, while 90 nm ZnO-NPs had the opposite effect. 16S rRNA gene sequencing showed that the species diversity and uniformity of root microorganisms exhibited contrasting trends with increasing ZnO-NPs size, with roots exposed to 50 nm ZnO-NPs showed higher species richness than those exposed to 30 nm or 90 nm. However, beneficial microorganisms such as Bryobacter and Methylophilus were inhibited by 90 nm ZnO-NPs. This study provides novel insights into a potential ZnO-NPs recycling strategy in soil using Agrostis stolonifera, offering a means to mitigate nanoparticle-induced damage to soil and crops.

Advances and Challenges in Tracking Interactions Between Plants and Metal-Based Nanoparticles

Metal-based nanoparticles (MNPs) are increasingly prevalent in the environment due to both natural processes and human activities, leading to direct interactions with plants through soil, water, and air exposure that can have beneficial and detrimental effects on plant growth and health. Understanding the uptake, translocation, and transformation of MNPs in plants is crucial for assessing environmental risks and leveraging nanotechnology in agriculture. However, accurate analysis of MNPs in plant tissues poses significant challenges due to complex plant matrices and the dynamic nature of nanoparticles. This short review summarizes recent advances in analytical methods for determining MNP-plant interactions, focusing on pre-processing and quantitative nanoparticle analysis. It highlights the importance of selecting appropriate extraction and analytical techniques to preserve nanoparticle integrity and accurate quantification. Additionally, recent advances in mass spectrometry, microscopy, and other spectroscopic techniques that improve the characterization of MNPs within plant systems are discussed. Future perspectives highlight the need to develop real-time in situ monitoring techniques and sensitive tools for characterizing nanoparticle biotransformation.

Multifaceted impacts of nanoparticles on plant nutrient absorption and soil microbial communities

With the growth of the global population and the increasing scarcity of resources, the sustainability and efficiency improvement of agricultural production have become urgent needs. The rapid development of nanotechnology provides new solutions to this challenge, especially the application of nanoparticles in agriculture, which is gradually demonstrating its unique advantages and broad prospects. Nonetheless, various nanoparticles can influence plant growth in diverse manners, often through distinct mechanisms of action. Beyond their direct effects on the plant itself, they frequently alter the physicochemical properties of the soil and modulate the structure of microbial communities in the rhizosphere. This review focuses intently on the diverse methods through which nanoparticles can modulate plant growth, delving deeply into the interactions between nanoparticles and plants, as well as nanoparticles with soil and microbial communities. The aim is to offer a comprehensive reference for the utilization of functionalized nanoparticles in the agricultural sector.

Plant Root Secretion Alleviates Carbamate-Induced Molecular Alterations of Dissolved Organic Matter

Studying the interaction between pesticide contamination in the plant system and the dissolved organic matter (DOM) composition is important to understand the impact of pesticides and plants on the ecological function of DOM. The present study investigated the effects of DOM on the bioaccumulation and biotransformation of carbamates in plants, carbamate exposure on DOM composition, and plant root secretion on the interaction between DOM and carbamates. The concentrations of carbamates and their metabolites in living cabbage plants were continuously tracked through an in vivo analytical method. The presence of DOM was found to reduce the highest bioconcentrations and shorten the time it took to reach the highest bioaccumulated amounts of isoprocarb and carbofuran in plants, while it showed no significant effect on the uptake behavior of carbaryl. DOM profiling results indicated that carbamate exposure substantially decreased the number and molecular diversity of DOM. Notably, plant root secretion alleviated carbamate-induced DOM molecular alterations by inducing a higher turnover rate of DOM compared to that in the uncontaminated group, highlighting the role of plants in mitigating the effects of exogenous pesticide exposure on DOM composition and maintaining DOM molecular homeostasis.

Electron-transfer-driven spatial optimisation of anaerobic consortia for efficient methanogenesis: Neglected inductive effect of conductive materials

The inductive effect of conductive materials (CMs) on enhancing methanogenesis metabolism has been overlooked. Herein, we highlight role of CMs in inducing the spatial optimisation of methanogenic consortia by altering the Lewis acid-base (AB) interactions within microbial aggregates. In the presence of CMs and after their removal, the methane production and methane proportion in biogas significantly increase, with no significant difference between the two situations. Analyses of interactions between CMs and extracellular polymer substances (EPSs) with and without D2O reveal that CMs promote release and transfer potential of electron in EPSs, which induce and enhance the role of water molecules being primarily as proton acceptors in the hydrogen bonding between EPSs and water, thereby changing the electron-donor- and electron-acceptor-based AB interactions. Investigations of succession dynamics of microbial communities, co-occurrence networks, and metagenomics further indicate that electron transfer drives the microbial spatial optimisation for efficient methanogenesis through intensive interspecies interactions.

Driving Role of Zinc Oxide Nanoparticles with Different Sizes and Hydrophobicity in Metabolic Response and Eco-Corona Formation in Sprouts (Vigna radiata)

Zinc oxide nanoparticles (ZnO NPs) cause biotoxicity and pose a potential ecological threat; however, their effects on plant metabolism and eco-corona evolution between NPs and organisms remain unclear. This study clarified the molecular mechanisms underlying physiological and metabolic responses induced by three different ZnO NPs with different sizes and hydrophobicity in sprouts (Vigna radiata) and explored the critical regulation of eco-corona formation in root-nano systems. Results indicated that smaller-sized ZnO inhibited root elongation by up to 37.14% and triggered oxidative burst and apoptosis. Metabolomics confirmed that physiological maintenance after n-ZnO exposure was mainly attributed to the effective stabilization of nitrogen fixation and defense systems by biotransformation of the flavonoid pathway. Larger-sized or hydrophobic group-modified ZnO exhibited low toxicity in sprouts, with 0.89-fold upregulation of citrate in central carbon metabolism. This contributed to providing energy for resistance to NP stress through amino acid and carbon/nitrogen metabolism, accompanied by changes in membrane properties. Notably, smaller-sized and hydrophobic NPs intensely stimulated the release of root metabolites, forming corona complexes with exudates. The hydrogen-bonded wrapping mechanism in protein secondary structure and hydrophobic interactions of heterogeneous functional groups drove eco-corona formation, along with the corona evolution intensity of n-ZnO > s-ZnO > b-ZnO based on higher (α-helix + 3-turn helix)/β-sheet ratios. This study provides crucial insight into metabolic and eco-corona evolution in bionano fates.

Nano molybdenum trioxide-mediated enhancement of soybean yield through improvement of rhizosphere soil molybdenum bioavailability for nitrogen-fixing microbial recruitment

Molybdenum (Mo) plays a pivotal role in the growth and nitrogen-fixing process of plants mediated by rhizobia. However, the influence of nano‑molybdenum trioxide (MoO3NPs) on soybean growth, rhizosphere bioavailable Mo, and nitrogen-fixing microorganisms remains underexplored. Here, we report that compared with that of ionic Mo and bulk MoO3, the utilization of MoO3NPs (specifically NPs0.05 and NPs0.15) significantly boosted the available Mo content in the rhizosphere soil throughout the seedling (by 21.64 %-101.38 %), podding (by 54.44 %-68.89 %), and mature stage (by 34.41 %-to 45.71 %) of soybean growth. Furthermore, both NPs0.05 and NPs0.15 treatments maintained consistently higher levels of acid-extractable Mo, reducible Mo, and oxidizable Mo across these stages, which facilitated stable conversion and supply of bioavailable Mo. Within the rhizosphere soil, NPs0.05 and NPs0.15 treatments resulted in the highest relative abundance of Rhizobiales and Bradyrhizobium genera, and significantly promoted the colonization of nitrogen-fixing microorganisms, thereby increasing the content of nitrate nitrogen (NO3--N) by 8.69 % and 7.72 % and ammonium nitrogen (NH4+-N) by 44.75 % and 17.55 %, respectively. Ultimately, these effects together contributed to 107.17 % and 84.00 % increment in soybean yield by NPs0.05 and NPs0.15 treatments, respectively. In summary, our findings underscore the potential of employing MoO3NPs to promote plant growth and maintain soil nitrogen cycling, indicating distinct advantages of MoO3NPs over ionic Mo and bulk MoO3.

Zinc oxide nanoparticles enhance plasmid transfer among growth-promoting endophytes in Arabidopsis thaliana

Nanoparticles (NPs) hold great promise for agricultural applications, yet their potential impact on exogenous gene transfer within plant remains poorly understood. In this study, we utilized the non-conjugative plasmid pCAMBIA1300, harboring the bialaphos resistance (bar) gene expressed in plant and the kanamycin resistance (kanR) gene as selectable marker in bacteria. Our results revealed a significant increase in the transfer of plasmid (via carrier Escherichia coli DH5α), both intra- and inter-species within the endophyte, when Arabidopsis thaliana was exposed to environmentally relevant level of zinc oxide (ZnO) NPs at a concentration of 0.7 μg/mL throughout its lifespan. Intriguingly, the plasmid exhibited selective transfer to growth-promoting endophytes, such as Enterobacter, Serratia, and Achromobacter, with the presence of ZnO NPs expanding the pool of potential recipients. This result is due to the facilitation of an endophytic and mutualistic lifestyle of invasive E. coli DH5α and the enrichment of beneficial bacteria aided by ZnO NPs. The plant's descendant generations did not express the bar gene, and the endophytes carrying the exogenous plasmid did not transmit it to sub sequent generation. This research provides crucial insights for assessing the potential risks associated with gene contamination and ensuring the safe and sustainable use of NPs in agriculture.