The application of biosynthesized nano-selenium fertilizers to crops can improve their nutrient levels by increasing their selenium content. However, microorganisms with a high selenite tolerance and rapid reduction rate accompanied with the production of selenium nanoparticles (SeNPs) at the same time have seldom been reported. In this study, a bacterial strain showing high selenite resistance (up to 300 mM) was isolated from a lateritic red soil and identified as Proteus mirabilis QZB-2. This strain reduced nearly 100% of 1.0 and 2.0 mM selenite within 12 and 18 h, respectively, to produce SeNPs. QZB-2 isolate reduced SeO₃^2– to Se⁰ in the cell membrane with NADPH or NADH as electron donors. Se⁰ was then released outside of the cell, where it formed spherical SeNPs with an average hydrodynamic diameter of 152.0 ± 10.2 nm. P. mirabilis QZB-2 could be used for SeNPs synthesis owing to its simultaneously high SeO₃^2– tolerance and rapid reduction rate.

Cadmium (Cd) pollution in rice and selenium (Se) deficiency in humans have attracted widespread attention. In this study, we investigated the effects of the combined application of biological nanoselenium (B-SeNPs) foliar spray and biochar (BC) on Se enrichment and Cd content reduction in rice. A pot experiment was established by designing four levels each of BC and B-SeNPs to be applied to rice plants. The results revealed that soil Cd bioavailability decreased by 3.26–16.67%, while soil Se bioavailability increased by 0.76–7.63% in the combined BC and B-SeNPs treatments, with rice photosynthesis showing significant enhancement during each growth period. Both BC and B-SeNPs treatments significantly enhanced the levels of antioxidant components (glutathione, phytochelatins, catalase, peroxidase, and superoxide dismutase) while reducing oxidative stress markers (malondialdehyde and superoxide anion radical) in rice leaves. Additionally, these treatments effectively modulated the subcellular distribution of Se and Cd, demonstrating their potential in alleviating Cd toxicity and enhancing Se homeostasis. These changes were accompanied by a marked reduction in lipid peroxidation (indicated by malondialdehyde) and superoxide radical accumulation, suggesting that BC and B-SeNPs treatments strengthened the antioxidative defense system in rice leaves. Additionally, compared with the BC0Se0 treatment, the combined application of BC and B-SeNPs significantly enhanced grain Se content by 7.14–221.43% while significantly reducing Cd content by 30.77–76.92%. The efficacy of grain Se enrichment and Cd reduction followed the sequence B-SeNPs + BC > Se only > BC only, where the BC5Se20 treatment demonstrated the most pronounced effects on both Se accumulation and Cd decrease in grains. Therefore, the combined application of foliar-applied B-SeNPs and biochar not only reduces Cd bioavailability in soil but also effectively suppresses Cd uptake by rice while simultaneously enhancing Se enrichment.

将“双耐”细菌与重金属富集植物——香根草构建修复体系，探讨其对铅（Pb）、镉（Cd）复合污染土壤的联合修复效应. 试验为双因素完全随机区组试验，A因素为铅镉污染浓度，设置6个水平，即Cd0Pb0、Cd10Pb400、Cd20Pb800、Cd40Pb1200、Cd60Pb1600、Cd80Pb2000（数据单位为mg/kg）. B因素为K7菌加菌量，设置3个水平，加菌量为0、1.5、3.0 g. 结果表明：（1）“双耐”细菌能提高香根草的生物量. 当处理为Cd10Pb400加菌1.5 g时，提高3.9%；当Cd40Pb1200加菌1.5 g时，提高13.2%，加菌量为3.0 g时增加30.46%；当Cd60Pb1600加菌1.5 g时，提高9.46%；当Cd80Pb2000加菌3.0 g时，提高7.02%. （2）“双耐”细菌对香根草地上和地下部铅、镉的吸收具有促进作用. 当土壤中铅含量< 1 200 mg/kg，加菌量1.5 g的香根草地上铅含量分别提高了1.9 mg/kg（Cd10Pb400）、3.6 mg/kg（Cd20Pb800）、4.1 mg/kg（Cd40Pb1200）. 对于镉而言，当加菌量为1.5 g时，地上部镉含量分别升高了314.7%（Cd10Pb400）、41.7%（Cd20Pb800）、35.1%（Cd20Pb800）、103.5%（Cd40Pb1200）、57.8%（Cd60Pb1600）. 加菌后根部铅含量大于不加菌的根部铅含量，Cd40Pb1200处理时，根部铅浓度最大. 相同铅、镉浓度处理时，加菌量为3.0 g的香根草根部镉含量比加菌量1.5 g的根部镉含量高. （3）加菌后的香根草根际土有效态铅、镉含量比不加菌的浓度低. 香根草根际土有效态铅含量下降幅度最大的处理是Cd20Pb800加菌1.5 g，与对照组相比降低了30.22%. 相同污染条件下，加菌3.0 g香根草根际土有效态镉含量最低. “双耐”菌强化香根草修复铅镉污染土壤的机理可为修复铅镉污染土壤的实际应用提供理论依据和技术参考. （图9 表2 参28）