[P004] Poster

1:00 PM - 1:50 PM JST(4:00 AM - 4:50 AM UTC)

[P02-222] Plant–microbe interactions drive rhizosphere nickel mobilization and phytoaccumulation in Artemisia spp.

○Mst Monjury Haque Choity¹, Suprokash Koner¹, Ning Han¹, Kasane Sato², Chihiro Inoue¹, Mei-Fang Chien¹ (1. Graduate School of Environmental Studies, Tohoku University, Sendai (Japan), 2. Honda R&D Co., Ltd, Wako (Japan))

Keywords:

Artemisia spp.; Nickel phytoaccumulation; Rhizospheric bacteria; Nickel bioavailability; Plant-microbe interactions

Nickel (Ni) is a critical metal essential for lithium-ion batteries in electric vehicles (EVs), and rapidly growing global demand has accelerated depletion of high-grade ore reserves, leaving predominantly low-grade ores and mining waste tailings that are difficult to process using conventional methods. Phytomining, the biological recovery of Ni using hyperaccumulator plants, offers a sustainable and cost-effective extraction strategy from such resources. However, phytomining efficiency remains limited by Ni bioavailability in the rhizosphere, which is dynamically regulated by plant–microbe interactions. Despite the recognized importance of these interactions, the specific microbial mechanisms driving Ni mobilization in native Japanese accumulator species remain poorly understood.This study investigated the interactions between Artemisia spp., a native Japanese Ni-accumulator, and its rhizospheric bacterial communities to determine their collective role in enhancing Ni bioavailability and enabling sustainable recovery from long-term contaminated soils. Soil samples were collected from a long-term contaminated industrial site in Japan. A two-month pot experiment was conducted under controlled conditions, growing Artemisia spp. in soils with varying Ni concentrations. Ni accumulation per unit dry biomass was estimated to assess phytoaccumulation efficiency, and rhizospheric bacterial communities were characterized through 16S rRNA-based amplicon sequencing.Sequential extraction analysis revealed that Ni accumulation in Artemisia spp. was positively correlated with the bioavailable Ni fraction (water soluble and exchangeable) in soil. Post cultivation soils exhibited increased Ni bioavailability alongside a decrease in soil pH, indicating that root-induced and microbial processes enhanced Ni mobilization in the rhizosphere. At the phylum level, th dominant bacterial groups were Pseudomonadota and Acidobacteriota, taxa known for their capacity to secret organic acids and siderophores that solubilize Ni. Functional predictions using PICRUSt2 (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) demonstrated significant enrichment of key metabolic genes (mdh, gltA and sdhA) involved in low-molecular-weight organic acid production. Collectively, these results suggest a mechanism whereby Artemisia-associated rhizobacteria enhance Ni bioavailability through organic acid-driven pH reduction, thereby increasing Ni phytoaccumulation efficiency. These findings advance our understanding of plant–microbe–metal interactions in contaminated soils and highlight the potential of harnessing indigenous rhizospheric communities to improve the efficiency and viability of Ni phytomining. Future studies to elucidate the interactions among Artemisia and its key rhizospheric bacteria will contribute to the successful Ni recovery from low-grade ores and mine tailings.