[P003] Poster

12:10 PM - 1:00 PM JST(3:10 AM - 4:00 AM UTC)

[P02-257] Evaluation of Soil Cd Solubilization Potential by Rhizobacteria of Arabidopsis halleri ssp. gemmifera

○Manato Shimizu¹, Christine Dwi Ariani Putri Wiyono¹, Motohiro Akashi¹, Seiichi Suzuki¹ (1. Faculty of Science and Technology, Seikei University, Tokyo (Japan))

Keywords:

Cd solubilization,Phytoremediation,Rhizobacteria

Phytoremediation is an environmentally friendly technique for removing heavy metals from contaminated soils; however, its efficiency depends on metal bioavailability such as cadmium (Cd). Therefore, enhancing Cd solubility in soil is one of the key factors for improving remediation efficiency. Although plants release root exudates that can solubilize Cd, this process is often limited under soil conditions. Chemical chelators and acids can enhance Cd soil solubility but may cause environmental risks such as groundwater contamination. Therefore, rhizobacteria that produce organic acids may offer a more environmentally compatible approach for enhancing Cd solubility.In this study, Cd-tolerant rhizosphere bacteria were isolated from A. halleri grown in Cd-contaminated soil in Tome City, Miyagi, Japan, and their potential roles in Cd mobilization and plant growth promotion were evaluated. Ten Cd-tolerant isolates were selected and identified by 16S rRNA analysis. To evaluate organic acid production, isolates were cultured in NBRIP medium, and organic acids were identified and quantified using UPLC. Subsequently, isolates with high organic acid production were subjected to pot experiments to assess soil acidification and Cd solubilization.Most of the isolates were identified as Pseudomonas sp. and were found to produce pyruvic acid (16.1–47.5 ppm) and malonic acid (420–1387 ppm). In contrast, one isolate identified as an Enterobacter sp. produced not only pyruvic acid (15.4 ppm) and malonic acid (520 ppm) but also a high concentration of citric acid (519 ppm), which was not detected in other isolates and is known for its strong chelating activity toward metal ions, thereby enhancing metal solubility in soils. In the pot experiment, the soil pH of the control treatment was 6.17, whereas the soil inoculated with Enterobacter sp. isolate showed a decreased pH of 5.95. Although the amount of available Cd in the soil did not show a marked change, the Cd concentration in plant tissues increased from 0.06 mg/g DW in the control to 0.136 mg/g DW in the inoculated treatment. This result suggests that the Enterobacter sp. may have enhanced Cd uptake without significantly altering bulk soil Cd fractions. Taken together, these findings indicate that Enterobacter sp. isolated from A. halleri is a promising rhizobacteria capable of improving Cd bioavailability to plants. This study demonstrates that rhizobacteria with organic acid production and Cd tolerance may contribute to controlled Cd mobilization, offering potential for sustainable phytoremediation strategies.