植物微生物是影响植物镉(Cd)吸收的重要因素。然而,在不同粒径的微塑料(MPs)的影响下,植物微生物群如何影响植物对Cd的吸收知之甚少。在这项研究中,在不同粒径的聚苯乙烯微塑料(PS-MPs)和Cd处理的影响下,通过16SrRNA基因的扩增子测序分析了小白菜根际和内圈的细菌结构和组装。结果表明,不同处理之间的芽内生菌没有显着差异。然而,与Cd处理相比,较大尺寸的PS-MPs(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-MPs(0.2μm)则没有。在较大尺寸的PS-MPs治疗下,根际细菌和根内生菌的生态位宽度显著增加。较大尺寸的PS-MPs也保持了细菌共现网络的稳定性和复杂性,而较小尺寸的PS-MP减少了它们。此外,与Cd处理相比,添加较大粒径的PS-MPs降低了均相截面的比例,同时增加了根系内生细菌群落组装中漂移的比例。较大尺寸的MPs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-MPs可以促进特定细菌分类群的定植,比如Brevundimonas,AKAU4049,SWB02,Ellin6055,卟啉杆菌,Sphingorhabdus,红杆菌属,红细菌,Devosia和其他一些属于α变形菌的细菌,在根际和根内圈。这些类群的定殖可以诱导根中生物膜的形成,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Cd的吸收。这项研究的结果为不同粒径的MPs对植物Cd吸收的影响的微生物机制提供了重要的见解。
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 Brevundimonas, AKAU4049, SWB02, Ellin6055, Porphyrobacter, Sphingorhabdus, Rhodobacter, Erythrobacter, Devosia 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.