Plant microbiota are an important factor impacting plant cadmium (Cd) uptake. However, little is known about how plant microbiota affects the Cd uptake by plants under the influence of microplastics (MPs) with different particle sizes. In this study, bacterial structure and assembly in the rhizosphere and endosphere in pakchoi were analyzed by amplicon sequencing of 16S rRNA genes under the influence of different particle sizes of polystyrene microplastics (PS-MPs) combined with Cd treatments. Results showed that there were no significant differences observed in the shoot endophytes among different treatments. However, compared to Cd treatment, larger-sized PS-MPs (2 and 20 μm) significantly increased community diversity and altered the structural composition of rhizosphere bacteria and root endophytes, while smaller-sized PS-MPs (0.2 μm) did not. Under the treatment of larger-sized PS-MPs, the niche breadth of rhizosphere bacteria and root endophytes were significantly increased. And larger-sized PS-MPs also maintained stability and complexity of bacterial co-occurrence networks, while smaller-sized PS-MPs reduced them. Furthermore, compared to Cd treatment, the addition of larger particle size PS-MPs decreased the proportion of homogeneous section, while increased the proportion of drift in root endophytic bacterial community assembly. The role of larger-sized MPs in the community assembly of rhizosphere bacteria was opposite. Using random forest and structural equation models, the study found that larger-sized PS-MPs can promote the colonization of specific bacterial taxa, such as and some other bacteria belonging to Alphaproteobacteria, in the rhizosphere and root endosphere. The colonization of these taxa can may induce the formation of biofilms in the roots, immobilize heavy metals through oxidation processes, and promote plant growth, thereby reducing Cd uptake by pakchoi. The findings of this study provide important insights into the microbial mechanisms underlying the influence of MPs with different particle sizes on plant Cd uptake.

中文翻译：

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不同粒径微塑料影响下植物微生物群与镉吸收的关系


植物微生物群是影响植物镉（Cd）吸收的重要因素。然而，人们对植物微生物群在不同粒径的微塑料（MP）的影响下如何影响植物对镉的吸收知之甚少。本研究通过16S rRNA基因的扩增子测序，分析了在不同粒径的聚苯乙烯微塑料（PS-MPs）结合Cd处理的影响下，小白菜根际和内圈的细菌结构和组装情况。结果表明，不同处理间地上部内生真菌没有显着差异。然而，与Cd处理相比，较大尺寸的PS-MP（2和20μm）显着增加了群落多样性，并改变了根际细菌和根内生菌的结构组成，而较小尺寸的PS-MP（0.2μm）则没有。在较大尺寸PS-MP的处理下，根际细菌和根内生菌的生态位宽度显着增加。较大尺寸的 PS-MP 还保持了细菌共生网络的稳定性和复杂性，而较小尺寸的 PS-MP 则降低了细菌共现网络的稳定性和复杂性。此外，与Cd处理相比，添加较大粒径的PS-MPs降低了根内生细菌群落组装中均质切片的比例，而增加了漂移的比例。较大尺寸的 MP 在根际细菌群落组装中的作用相反。使用随机森林和结构方程模型，研究发现较大尺寸的 PS-MP 可以促进特定细菌类群的定植，例如属于 Alphaproteobacteria 的一些其他细菌在根际和根内圈的定植。 这些类群的定植可以诱导根部生物膜的形成，通过氧化过程固定重金属，促进植物生长，从而减少小白菜对镉的吸收。这项研究的结果为了解不同粒径的 MPs 对植物镉吸收影响的微生物机制提供了重要的见解。