Purpose

An important bottleneck in phytoremediation technologies, which focus on extraction of potentially toxic trace elements, is the low solubility and bioavailability of metals, a handicap that worsens over time. To overcome this barrier, we explored the possibility of using Zn-solubilising bacteria with plant growth-promoting characteristics.

Material and methods

Zn-tolerant soil bacteria were isolated from an ancient Zn-Pb mine using cultivation media with a high ZnSO₄ concentration (2.5 mM). Among the bacteria able to grow on this medium, those with plant growth-promoting (PGP) characteristics (P and Zn solubilisation and indole-3-acetic acid production) were selected. The best candidates (seven strains) were identified after 16S rDNA sequencing, and Pseudomonas fluorescens NCBI Accession No. MT218317 was selected for a microbial-assisted phytoremediation experiment with Sinapis alba plants.

Results and discussion

Fifteen days after inoculation, both shoot and root growth were higher in inoculated than in un-inoculated white mustard plants. Soil metal contents (total and exchangeable fractions) remained practically invariable. In contrast, the PGP bacterium raised the plant concentrations of some of the micronutrients, together with Cd and Pb. In addition, the bioaccumulation factors for Cd and Zn were higher in the bacterium-inoculated plants. Increased metal concentrations in plants on bacterium-inoculated soil can be due to either or both bacterium-induced enhancement of micronutrients availability and production of beneficial compounds induced by the bacterium.

Conclusions

The artificial inoculation of P. fluorescens MT218317 promoted the biomass of S. alba plants potentiating the phytoextraction of Zn and phytostabilisation of Cd and Pb on a metal-contaminated soil. The novelty of the study is the use of metal-solubilising microorganism in combination with metal-tolerant plants for improving the restoration of soils containing potentially toxic elements.

中文翻译：

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来自矿井土壤的天然锌增溶细菌促进植物生长并促进植物修复

目的

植物修复技术的一个重要瓶颈是金属的低溶解度和生物利用度，该技术着重于潜在有毒微量元素的提取，这一障碍随着时间的推移而恶化。为了克服这一障碍，我们探索了使用具有促进植物生长特性的增锌细菌的可能性。

材料与方法

使用高浓度ZnSO ₄（2.5 mM）的培养基从古老的Zn-Pb矿中分离出耐锌的土壤细菌。在能够在这种培养基上生长的细菌中，选择具有植物生长促进（PGP）特性（P和Zn增溶以及吲哚-3-乙酸生成）的细菌。在对16S rDNA进行测序后，确定了最佳候选菌株（7个菌株），并选择了荧光假单胞菌NCBI登录号MT218317来进行白芥（Sinapis alba）植物的微生物辅助植物修复实验。

结果与讨论

接种后十五天，接种后的芽和根生长均高于未接种的白芥菜植株。土壤金属含量（总和可交换部分）实际上保持不变。相反，PGP细菌与Cd和Pb一起提高了某些微量营养素的植物浓度。另外，细菌接种植物中Cd和Zn的生物蓄积因子较高。细菌接种的土壤中植物中金属浓度的增加可能是由于细菌诱导的微量营养素利用率的提高或由细菌诱导的有益化合物的产生所致。

结论

人工接种荧光假单胞菌MT218317促进了白假丝酵母植物的生物量，从而在金属污染的土壤上增强了锌的植物提取以及Cd和Pb的植物稳定作用。这项研究的新颖性是将金属增溶微生物与耐金属植物结合使用，以改善土壤中含有潜在毒性元素的恢复。