Abstract

The rhizobia isolated from root nodules of horse gram were screened for nickel (Ni) tolerance in vitro. The strain HGR-4 could tolerate 1000 µg g⁻¹ of Ni. It was also observed that horse gram plants associated with HGR-4 have shown Ni stress tolerance in Ni amended soils up to a concentration of 100 µg g⁻¹. In another experiment, the plants associated with HGR-4 have shown higher nodulation, nitrogen level, and leghaemoglobin content at 80 µg g⁻¹ of Ni than control plants without HGR-4 inoculation. Analysis of biosorption potential of Ni in horse gram plants inoculated by the strain HGR-4 was done using atomic absorption spectroscopy revealed maximum biosorption in bacterial root nodules. Besides, there was a reduction in the content of the heavy metal in the soil samples which demonstrates a fair amount of heavy metal extraction and accumulation of Ni by rhizobia associated root nodules of the horse gram. This study demonstrates that the strain HGR-4 (GQ483457 Rhizobium sp. ATCC BAA-2335) could be a potential source for phytoextraction of Ni contaminated soils upon its association with horse gram. The study could be of use in phytoremediation of metal (Ni) contaminated soils in the future.

Novelty statement: The phytoremediation of nickel (Ni) using of rhizobia associated with horse gram remains unevaluated till now. Horse gram associated with rhizobia could produce nodules and fix nitrogen even in Ni amended soils. The biosorption potential of the rhizobial strains was analyzed from both root nodules and soil. These findings imply that horse gram plants associated with these rhizobial strains could be used to remediate Ni metal in contaminated soils.

摘要

对从马革兰根瘤中分离的根瘤菌进行体外镍 (Ni) 耐受性筛选。菌株HGR-4 可耐受1000 µg g ^-1的Ni。还观察到与 HGR-4 相关的马革兰植物在 Ni 修正的土壤中显示出 Ni 胁迫耐受性，最高浓度为 100 µg g ^-1。在另一个实验中，与 HGR-4 相关的植物在 80 µg g ^{-1 时}表现出更高的结瘤、氮水平和豆血红蛋白含量Ni 的含量高于未接种 HGR-4 的对照植物。使用原子吸收光谱法对接种 HGR-4 菌株的马革兰植物中 Ni 的生物吸附潜力进行分析，结果显示细菌根瘤中的生物吸附最大。此外，土壤样品中重金属的含量有所减少，这表明马革兰根瘤菌相关的根瘤提取和积累了大量的重金属镍。该研究表明，菌株 HGR-4（GQ483457根瘤菌属种 ATCC BAA-2335）在与马革兰氏菌结合后可能成为对 Ni 污染土壤进行植物提取的潜在来源。该研究未来可用于金属（Ni）污染土壤的植物修复。

新颖性声明：迄今为止，与马革兰氏菌相关的根瘤菌对镍 (Ni) 的植物修复尚未得到评估。即使在镍改良的土壤中，与根瘤菌相关的马革兰也能产生根瘤和固氮。从根瘤和土壤中分析了根瘤菌菌株的生物吸附潜力。这些发现意味着与这些根瘤菌菌株相关的马革兰植物可用于修复受污染土壤中的镍金属。