Sedum alfredii (Crassulaceae) is a promising model plant for Cd/Zn phytoextraction, with potential for leveraging its rhizosphere microbiomes to help improve phytoremediation efficiency and enhance their use. Here, we investigated the successional trajectories, assembly rules and co-occurrence networks of archaeal and bacterial rhizosphere microbiomes of S. alfredii over three growing seasons. 16S rRNA gene profiling showed that rhizosphere microbiota exhibited a pattern of succession that was repeatable and consistent over seasons in soils with varying concentrations of Cd/Zn. Plant roots selectively enriched α-, β- and γ-Proteobacteria, Halobacteria (Euryarchaeota) and Thermoprotei (Crenarchaeota) over seasons. Taxa that had increased relative abundance in rhizosphere showed phylogenetic clustering (closely related species share suite of traits necessary to persist in the rhizosphere), suggesting some conserved traits were selected by plants. A neutral community model predicted that successional pattern of rhizosphere microbiota was increasingly driven by non-neutral processes, such as microbial interactions or host selection. Rhizosphere co-occurrence networks were less complex than the bulk soil networks, indicating that prolonged phytoextraction could decrease microbial network complexity. The proportion of positive characteristics within rhizosphere co-occurrence networks dramatically increased from the first season (79%) to the third season (84%), whereas bulk soil networks showed an opposing trend (from 57% to 42%), suggesting that rhizosphere had a greater potential for mutualistic interactions between co-existing microorganisms. A shift in rhizosphere network structure was also significantly associated with shoot biomass and Cd/Zn accumulation. Our results demonstrated that S. alfredii consistently recruits soil microbes that are proficient in phytoextraction to its root environment, and results can serve as a basis for designing treatments that specifically promote effective bioremediating communities.

Sedum alfredii（景天科）是一种有前途的镉/锌植物提取示范植物，具有利用其根际微生物群帮助提高植物修复效率和提高其利用潜力的潜力。在这里，我们调查了三个生长季节中S. alfredii的古细菌和细菌根际微生物群落的连续轨迹，组装规则和共现网络。16S rRNA基因图谱显示，根际微生物群在不同Cd / Zn浓度的土壤中表现出可重复且连续的连续演替模式。在各个季节中，植物根部选择性地富集α-，β-和γ-变形杆菌，盐杆菌（Euryarchaeota）和嗜热变形菌（Crenarchaeota）。根际中相对丰度增加的类群显示出系统发生聚类（密切相关的物种共有在根际中持续存在所必需的一系列性状），表明植物选择了一些保守性状。中性群落模型预测，根际微生物群的演替模式越来越多地受到非中性过程（如微生物相互作用或宿主选择）的驱动。根际共生网络不如整体土壤网络复杂，表明延长的植物提取可以降低微生物网络的复杂性。从第一季（79％）到第三季（84％），根际共生网络中积极特征的比例急剧增加，而散装土壤网络则呈现相反的趋势（从57％增加到42％），这表明，根际微生物在共存微生物之间具有更大的相互影响的潜力。根际网络结构的变化也与芽生物量和Cd / Zn积累显着相关。我们的结果表明，S。alfredii持续吸收能够将植物提取到其根部环境的土壤微生物，其结果可作为设计专门促进有效生物修复群落的处理的基础。