Purpose

The success of phytoremediation relies on beneficial plant-microbe interactions. However, the changes of soil microbiota, during the phytoremediation of ion-adsorption rare earth element (REE) mine tailings, are far from understood. The present study was conducted to reveal the co-occurrence patterns and key regulating factors of bacterial communities in ion-adsorption REE mine tailings with phytoremediation.

Materials and methods

A field experiment was conducted on an ion-adsorption REE mine tailing to test three phytoremediation strategies: (i) phytostabilization with grasses, (ii) phytostabilization with economic crops, and (iii) phytoextraction with REE hyperaccumulators. The bacterial community diversity, co-occurrence patterns, and the key regulating environmental factors in bulk and rhizospheric soils after 16 months of reclamation were studied by 16S Illumina high-throughput sequencing.

Results and discussion

The soils of plots with REEs-hyperaccumulators had significantly higher α-diversity than those planted with non-accumulators. After phytoremediation, the diversity and relative abundances of bacteria assisting in nutrient acquisition pronouncedly increased in the bulk soil of the reclaimed plots. Some plant growth–promoting bacteria (PGPB), e.g., Rhodanobacter, Streptomyces, and Bacillus, were enriched in the rhizospheric soil samples. Meanwhile, soil nutrient (total carbon and total nitrogen) concentration and REE availability were the most significant factors shaping the bacterial communities. Furthermore, special bacterial consortia of Bacilli took up the positions of the keystone species.

Conclusions

The results revealed the co-occurrence patterns and key regulating factors of bacterial communities in ion-adsorption REE mine tailings, which will provide more crucial information for the optimization of the reclamation of REE tailings.

中文翻译：

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用有机改良剂和植物进行的填海工程重塑了离子吸附稀土元素矿山尾矿中细菌群落的多样性和结构。

目的

植物修复的成功取决于有益的植物-微生物相互作用。然而，在离子吸附稀土元素（REE）矿尾矿的植物修复过程中，土壤微生物区系的变化远未了解。本研究旨在揭示离子修复稀土离子尾矿中植物群落的共生模式和关键调控因子。

材料和方法

在离子吸附稀土矿尾矿上进行了田间试验，以测试三种植物修复策略：（i）用草进行植物稳定化，（ii）用经济作物进行植物稳定化，以及（iii）使用稀土超富集剂进行植物提取。通过16S Illumina高通量测序研究了开垦16个月后散装和根际土壤中的细菌群落多样性，共现模式以及关键的调控环境因素。

结果和讨论

REEs-高蓄积地块土壤的α-多样性明显高于非蓄积的土壤。植物修复后，在开垦土地的大块土壤中，有助于营养获取的细菌的多样性和相对丰度明显增加。一些植物生长促进细菌（PGPB），例如，Rhodanobacter，链霉菌，和芽孢杆菌属，根际土壤样品中富集。同时，土壤养分（总碳和总氮）浓度和REE利用率是影响细菌群落的最重要因素。此外，芽孢杆菌的特殊细菌群落占据了基石种的位置。

结论

结果揭示了离子吸附稀土尾矿中细菌群落的共生模式和关键调控因子，为优化稀土尾矿的复垦提供了更为关键的信息。