Rhizosphere bacterial community dynamics of the cadmium hyperaccumulator Sedum plumbizincicola under a cadmium concentration gradient during phytoextraction

Abstract

The rhizosphere microbiome plays an important role in plant growth and behavior during phytoremediation. This work aims to explore how hyperaccumulating plant performance (shoot biomass and Cd uptake) and rhizosphere bacterial community are driven by plant development under a Cd concentration gradient and their relationship during plant growth. A pot experiment was conducted using the Cd hyperaccumulator Sedum plumbizincicola grown in soil spiked with 0, 5 and 20\xa0mg Cd kg−1 for 13\xa0weeks. Plant performance (shoot biomass and Cd uptake) was determined and the rhizosphere bacterial community was examined by weekly Illumina sequencing. Biomarker genera were identified by the Random Forest model and the functions were predicted by PICRUSt2. The rhizospheres bacterial community tended to stabilize from the 6th or 7th week regardless of the soil Cd concentration, coinciding with the vigorous growth stage of the hyperaccumulator. Biomarker genera Paenibacillus and Streptacidiphilus enriched in the stable stage showed significant positive correlations with Cd uptake. In addition, some predicted gene abundances of enzymes related to plant growth promotion by the rhizosphere bacterial community were influenced to various degrees by plant development and soil Cd concentration. There exists a stable bacterial community in the rhizosphere of S. plumbizincicola during phytoremediation and biomarker taxa enriched at this stage were positively correlated with Cd uptake. Selecting microorganisms that match the developmental stages might further enhance phytoremediation. This provides some theoretical basis for modulating rhizosphere microbes at the appropriate time during phytoextraction to optimize the phytoremediation technique.