耐砷促生菌对超富集植物蜈蚣草砷吸收及根际微生物群落的调控作用

Effects of arsenic-tolerant growth-promoting bacteria on arsenic uptake and rhizosphere microbial community of hyperaccumulator Pteris vittata

摘要:

【目的】分析添加外源促植物生长微生物(plant growth-promoting bacteria, PGPB)对植物生长、砷富集和根际微生物的影响，为植物-微生物联合修复砷污染土壤提供参考。【方法】通过添加外源PGPB，研究蜈蚣草生物量和砷富集量与外源微生物促植物生长特性的关系，采用高通量测序技术分析蜈蚣草根际微生物群落在外源PGPB干预下的变化规律。【结果】2株根际菌(假单胞菌PG12、芽孢杆菌R19)和1株内生菌(恶臭假单胞菌S6)具备典型的促植物生长特性，对蜈蚣草的促生作用顺序为：PG12>S6>R19，与对照组相比，生物量分别提高了234% (P<0.01)、136% (P<0.01)和67%；添加外源PGPB后，蜈蚣草砷含量从对照的18.50 mg提高到了31.25−46.95 mg，增幅高达153% (PG12)和139% (S6)，对应的蜈蚣草砷浓度从2 616.34 mg/kg降至1 348.04−2 156.23 mg/kg，呈现出典型的砷“稀释效应”；α多样性指数Sobs、Chao和Ace显示，仅R19处理显著提高了根际微生物的群落多样性，而β多样性指数PCA、PCoA和PLS-DA表明各处理组之间均存在较明显的聚类差异；物种组成分析表明，外源PGPB影响了蜈蚣草根际微生物群落的分布，表现为Arthrobacter、Solirubrobacter等群落相对丰度的增加和Acidibacter、Dongia、MND1等群落相对丰度的减少，这些菌群可能与蜈蚣草生长和砷吸收有关。【结论】外源添加PGPB对蜈蚣草生长、砷吸收和根际微生物群落均有显著调节效应，此结果可为揭示微生物强化植物砷修复的机制并为促进植物-微生物联合修复砷污染土壤的相关研究提供参考。

Abstract:

[Objective] To analyze the effects of the addition of exogenous plant growth-promoting bacteria (PGPB) on plant growth, arsenic (As) accumulation, and rhizosphere microorganisms, and provide references for plant-microbial remediation of As-contaminated soil. [Methods] By adding exogenous PGPB into the soil, the relationships between the plant biomass and As content of Pteris vittata and the plant growth-promoting characteristics of PGPB were investigated. The high-throughput sequencing was also used to analyze the change in the rhizosphere microbial community of P. vittata with the intervention of exogenous PGPB. [Results] Two rhizobacteria Pseudomonas sp. PG12 and Bacillus sp. R19, and one endophytic bacterium P. putida S6 had typical plant growth-promoting characteristics, and the order of the growth-promoting effects on P. vittata was PG12>S6>R19. As compared with the control group, PG12, S6, and R19 increased the plant biomass by 234% (P<0.01), 136% (P<0.01), and 67%, respectively. The addition of exogenous PGPB increased the As content of P. vittata from 18.50 mg to 31.25−46.95 mg, being an increased percentage of 153% in PG12 and 139% in S6, respectively. The corresponding concentration of As in P. vittata decreased from 2 616.34 mg/kg to 1 348.04−2 156.23 mg/kg, showing a typical As “dilution effect”. Moreover, the α diversity indexes including Sobs, Chao, and Ace revealed that only R19 significantly improved the diversity of the rhizosphere microbial community, while the beta diversity analysis based on principal component analysis (PCA), principal co-ordinates analysis (PCoA), and partial least squares-discriminant analysis (PLS-DA) showed that there were significant clustering differences among all treatments. Furthermore, species composition analysis showed that the exogenous PGPB affected the distribution of the rhizosphere microbial community with an increase in the relative abundance of Arthrobacter and Solirubrobacter, etc., and a decrease in the relative abundance of Acidibacter, Dongia, and MND1. These microbial communities were presumedly associated with the growth and As uptake of P. vittata. [Conclusion] Exogenous PGPB addition shows positive effects on the growth, As uptake, and rhizosphere microbial community of P. vittata. The results of this study provide important clues for revealing the mechanism of arsenic remediation enhanced by microorganisms in plants, thereby promoting the associated studies on the plant-microbial remediation of As-contaminated soil.