产多胺细菌调控根际细菌群落阻控小麦Cd吸收效应

Polyamine-producing Bacteria Regulated the Community Structure of Rhizosphere Bacteria and Reduced the Absorption of Cd in Wheat

土壤中的一些功能微生物能够通过吸附和沉淀等作用固定重金属,降低其有效态含量,从而阻控作物对重金属的吸收,在中轻度重金属超标农田钝化修复中发挥着重要作用.通过盆栽试验,借助高通量测序技术研究外源产多胺细菌Bacillus sp.N3的接种对小麦Cd吸收和根际土壤细菌群落组成和功能的影响.结果表明,与不接菌对照相比,菌株N3能够显著降低小麦籽粒中Cd(64.7%)和根际土壤DTPA-Cd(50.1%)的质量分数,提高根际土壤pH值(由6.84升高到6.97)和多胺的含量.高通量测序结果表明,菌株N3的接种降低了小麦根际土壤细菌群落的多样性,但是提高了β-Proteobacteria、Bacteroidetes和Firmicutes的相对丰度.与此同时,菌株N3显著提高了小麦根际土壤中具有重金属固定和植物促生能力的菌属的相对丰度(主要为:Bacillus、Arthrobacter、Brevundimonas、Ensifer、Pedobacter、Rhizobium、Pseudomonas、Enterobacter和Serratia).PICRUSt功能预测表明,菌株N3显著提高了小麦根际土壤中参与抗氧化能力、激素合成和硫代谢的基因拷贝数.以上结果表明,产多胺细菌N3通过提高小麦根际土壤的pH值、多胺含量、具有重金属固定或者植物促生细菌等功能菌株和参与抗氧化能力、激素合成和硫代谢等代谢途径的细菌群落丰度来降低根际土壤中DTPA-Cd的含量,进而阻控了小麦对Cd的吸收.结果可为重金属超标农田修复和保障小麦安全生产提供理论依据和技术支撑.

Some functional microorganisms in the soil immobilize heavy metals by adsorption and precipitation, prevent the absorption of heavy metals by crops, and play an important role in the passivation and remediation of medium and mild heavy metal^(-)contaminated soil. A pot experiment was conducted to study the effects of the exogenous polyamine-producing bacterium Bacillus sp. N3 on Cd uptake and the bacterial community composition and function in the rhizosphere soil. The results showed that strain N3 significantly reduced the contents of Cd(64.7%) in wheat grain and DTPA-Cd(50.1%) in rhizosphere soil and increased the pH(from 6.84 to 6.97) and polyamine content. High-throughput sequencing results showed that inoculation of strain N3 reduced the diversity of the bacterial community;however, it increased the relative abundances of β-Proteobacteria, Bacteroidetes, and Firmicutes in wheat rhizosphere soil. Meanwhile, strain N3 also increased the relative abundances of heavy metal^(-)immobilizing bacteria and plant growth-promoting bacteria(Bacillus,Arthrobacter,Brevundimonas,Ensifer,Pedobacter,Rhizobium,Pseudomonas,Enterobacter, and Serratia) in wheat rhizosphere soil. The PICRUSt function prediction showed that strain N3 increased the copy number of genes involved in antioxidant capacity, hormone synthesis, and sulfur metabolism in wheat rhizosphere soil. These results indicated that the polyamine-producing bacteria N3 reduced the DTPA-Cd content by increasing the pH;the polyamine contents;the abundances of bacteria with heavy metal^(-)immobilizing or plant growth-promoting traits;and the metabolic pathway involved in antioxidant capacity, hormone synthesis, and sulfur metabolism in wheat rhizosphere soil, thus inhibiting the absorption of Cd by wheat. The results provide theoretical basis and technical support for restoring farmland with excessive heavy metals and ensuring the safe production of wheat.