Arsenic modifies the microbial community assembly of soil–root habitats in <i>Pteris vittata</i>

<i>Pteris vittata</i>, renowned for its ability to hyperaccumulate arsenic, presents a promising solution to the escalating issue of global soil arsenic contamination. This fern cultivates a unique underground microbial community to enhance its environmental adaptability. However, our understanding of the assembly process and the long-term ecological impacts of this community remains limited, hindering the development of effective soil remediation strategies. This study addresses this gap by investigating soil-root habitats from three geographically diverse fields comprising a gradient of arsenic contamination, complemented by a time-scale greenhouse experiment. Field investigations reveal that arsenic stress influences community assembly dynamics in the rhizosphere by enhancing processes of homogeneous selection. Greenhouse experiments further reveal that arsenic exposure alters the assembly trajectory of rhizosphere communities by promoting key microbial modules. Specifically, arsenic exposure increases the enrichment of a core taxon (i.e. <i>Rhizobiaceae</i>) in the rhizosphere, both in field and greenhouse settings, boosting their abundance from undetectable levels to 0.02% in the soil after phytoremediation. Notably, arsenic exposure also promotes a pathogenic group (i.e. <i>Spirochaetaceae</i>) in the rhizosphere, increasing their abundance from undetectable levels to 0.1% in the greenhouse. This raise concerns that warrant further investigation in future phytoremediation studies. Overall, this study elucidates the assembly dynamics of the soil microbiome following the introduction of a remediation plant and emphasizes the often-overlooked impacts on soil microbial community following phytoremediation. By probing the ecological impacts of remediation plants, this work advances a more nuanced understanding of the complex ecological implications inherent in phytoremediation processes.