Key biomarkers associated with nitrogen fixation in rhizosphere soil affect Cd accumulation in Sedum plumbizincicola

Since some key microbial biomarkers could be selectively recruited and enriched into the rhizosphere of different plants under heavy metal stress, exploring their role may be helpful for the remediation of heavy metal pollution. Herein, microbial communities in the bulk and rhizosphere (Barley, Brassica napus L ., Sedum plumbizincicola , Geranium carolinianum and Cnidium monnieri ) soils contaminated with cadmium (Cd) were analyzed by coupling high-throughput sequencing and qPCR. Results showed that differences in microbial diversity were insignificant between bulk and rhizosphere soils, whose bacterial community was associated more with the environmental characteristics than the fungal community. Notably, the networks revealed several key biomarkers among different plants plant species associated with nitrogen fixation. Moreover, these identified key biomarkers were capable of conferring Cd tolerance and siderophore production. Rhizobium sp. WW22, Burkholderia sp. WW13, and Pseudomonas sp. WW2 obtained from the hyperaccumulator S. plumbizincicola exhibited high nitrogenase activity and substantially augmented its plant growth and nitrogen uptake. In particular, Burkholderia sp. WW13 significantly increased Cd accumulation in shoots of S. plumbizincicola , which would provide a more effective strategy for Cd remediation. This study demonstrated that the tested key biomarkers could bolster the growth of hyperaccumulator plants and enhance Cd enrichment efficiency, providing a promising new strategy for pollution remediation of soils. • Long-term Cd stress led to similar key biomarkers in rhizosphere soil of different plants • Key biomarkers with Cd tolerance and N fixation promoted Sedum plumbizincicola growth • Burkholderia sp. WW13 enhanced bioconcentration factor of Cd in S. plumbizincicola shoots