[P003] Poster

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

[P02-239] Isolation and Characterization of a Sr²⁺-Tolerant Glutamicibacter sp. Exhibiting Cell Aggregation and Strontium Recovery

○Tomoka Tsuchikawa¹, Yuki Handa², Masahiro Ito^1,2,3 (1. Graduate School of Life Sciences, Toyo University (Japan), 2. Faculty of Life Sciences, Toyo University (Japan), 3. Toyo University Bio-Resilience Research Project (BRRP) (Japan))

Keywords:

Strontium(Sr),Bioremediation,Environmental microbiology

[Purpose]
Strontium (Sr) is an alkaline earth metal widely distributed in nature, and some of its radioactive isotopes are recognized as environmental contaminants. ⁹⁰Sr, which has a long half-life, is considered a major problematic radionuclide in radioactive pollution. Although chemical methods are commonly used for Sr removal, they present challenges such as high treatment costs and secondary waste generation. In contrast, microbial metal adsorption and accumulation have attracted attention as environmentally friendly and sustainable approaches in chemical biotechnology and bioremediation, with relevance to the SDGs. However, knowledge of Sr-tolerant bacteria remains limited. Therefore, this study aimed to isolate Sr²⁺-tolerant bacteria from natural environmental samples and evaluate their potential for Sr²⁺ recovery.
[Methods]
Bacterial strains were screened from soil, moss, and river water samples using media containing Sr²⁺. The isolates were tested for tolerance to high concentrations of Sr²⁺, and representative strains were identified by 16S rRNA gene analysis. Among them, a strain showing marked cell aggregation under Sr²⁺-containing conditions was selected for further study. Its growth under Sr²⁺ stress, morphological changes following Sr²⁺ exposure, and ability to recover Sr²⁺ from the medium were evaluated.
[Results]
Several bacterial strains capable of growing under high Sr²⁺ concentrations were isolated from environmental samples. Among them, strain YT-2, identified as Glutamicibacter sp., exhibited remarkable cell aggregation in the presence of Sr²⁺. This strain was able to grow under high Sr²⁺ concentrations and showed changes in cell surface structures after Sr²⁺ exposure. In recovery experiments, the Sr²⁺ concentration in the medium decreased after treatment with YT-2 cells, indicating that this strain can remove Sr²⁺ from the surrounding environment.
[Discussion]
The decrease in Sr²⁺ concentration suggests that YT-2 adsorbs Sr²⁺ onto the cell surface and/or extracellular matrix. The aggregation phenotype and structural changes observed under Sr²⁺-containing conditions further support the involvement of cell surface-associated mechanisms in Sr²⁺ interaction. These findings indicate that naturally derived Sr²⁺-tolerant bacteria can serve as useful microbial resources for Sr recovery. From a chemical biotechnology perspective, this microbial system may provide an environmentally benign alternative or complement to conventional chemical treatment methods.
[Conclusion]
This study demonstrated that a naturally isolated Glutamicibacter sp. YT-2 possesses both high Sr²⁺ tolerance and Sr²⁺ recovery capability. The results suggest that Sr²⁺-tolerant bacteria have significant potential for sustainable strontium recovery and bioremediation. Further studies on process optimization and mechanism elucidation will support the development of practical, low-environmental-impact technologies aligned with SDG-oriented resource and environmental management.