Nickel oxide nanoparticles (NiO-NPs) pose potential threats to agricultural production. Bacillus subtilis has emerged as a stress-mitigating microbe that alleviates the phytotoxicity caused by NiO-NPs. However, the mechanisms underlying its effectiveness, particularly in root-nodule symbiosis and biological N2-fixation (BNF), remain unclear. Here, we tested the combined exposure of NiO-NPs (50 mg kg−1) and B. subtilis on soybean (Glycine max L.) growth and BNF. Combined exposure increased root length, shoot length, root biomass, and shoot biomass by 19% to 26%, while Ni (200 mg kg−1) reduced them by 38% to 53% compared to the control. NiO-NPs at 100 and 200 mg kg−1 significantly (P < 0.05) reduced nodule formation by 16% and 58% and Nitrogen assimilation enzyme activities levels (urease, nitrate reductase, glutamine synthetase, and glutamate synthetase) by 13% to 57%. However, co-exposure with B. subtilis improved nodule formation by 22% to 44%. Co-exposure of NiO-NPs (200 mg kg−1) with B. subtilis increased peroxidase, catalase, and glutathione peroxidase activity levels by 20%, 16%, and 14% while reducing malondialdehyde (14%) and hydrogen peroxide (12%) levels compared to NiO-NPs alone. Additionally, co-exposure of NiO-NPs (100 and 200 mg kg−1) with B. subtilis enhanced the relative abundance of Stenotrophomonas, Gemmatimonas, and B. subtilis, is associated with N2-cycling and N2-fixation potential. This study confirms that B. subtilis effectively mitigates NiO-NP toxicity in soybean, offering a sustainable method to enhance BNF and crop growth and contribute to addressing global food insecurity.

中文翻译：

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氧化镍纳米材料和枯草芽孢杆菌对大豆生长和氮同化动力学的共暴露影响


氧化镍纳米颗粒 （NiO-NPs） 对农业生产构成潜在威胁。枯草芽孢杆菌已成为一种缓解压力的微生物，可减轻 NiO-NPs 引起的植物毒性。然而，其有效性的潜在机制，特别是在根瘤共生和生物 N2 固定 （BNF） 中，仍不清楚。在这里，我们测试了 NiO-NPs （50 mg kg-1） 和枯草芽孢杆菌对大豆 （Glycine max L.） 生长和 BNF 的联合暴露。与对照相比，联合暴露使根长、芽长、根生物量和芽生物量增加了 19% 至 26%，而 Ni （200 mg kg-1） 将它们减少了 38% 至 53%。100 和 200 mg kg-1 的 NiO-NPs 显着降低了 16% 和 58% 的结节形成，并将氮同化酶活性水平（脲酶、硝酸盐还原酶、谷氨酰胺合成酶和谷氨酸合成酶）降低了 13% 至 57%。然而，与枯草芽孢杆菌的共同暴露将根瘤形成改善了 22% 至 44%。与单独的 NiO-NP 相比，NiO-NPs （200 mg kg-1） 与枯草芽孢杆菌的共同暴露使过氧化物酶、过氧化氢酶和谷胱甘肽过氧化物酶活性水平提高了 20%、16% 和 14%，同时降低了丙二醛 （14%） 和过氧化氢 （12%） 水平。此外，NiO-NPs（100 和 200 mg kg-1）与枯草芽孢杆菌的共同暴露增强了狭窄嗜血单胞菌、Gemmatimonas 和枯草芽孢杆菌的相对丰度，与 N2 循环和 N2 固定电位有关。本研究证实，枯草芽孢杆菌有效减轻大豆中的 NiO-NP 毒性，提供了一种可持续的方法来促进 BNF 和作物生长，并为解决全球粮食不安全问题做出贡献。