Speaker
Description
Barium (Ba) and strontium (Sr) are non-essential, potentially toxic elements frequently associated with radioactive waste from abandoned uranium mines. Their chemical similarity to alkaline earth metals, particularly calcium (Ca), enables biological substitution that may disrupt cellular processes in living organisms. Despite their environmental relevance, microbial tolerance mechanisms toward Ba and Sr remain insufficiently characterized. This study investigates the diversity and metal tolerance of bacteria inhabiting a wetland ecosystem impacted by historical uranium mining.
Inductively coupled plasma mass spectrometry (ICP-MS) detected Ba and Sr, together with U and other trace elements, in rhizosphere of Scirpus sylvaticus collected from the rhizosphere of a wetland downstream of the former uranium mine at Zadní Chodov, Czech Republic. High-throughput 16S rRNA gene analysis revealed a microbial community dominated by Proteobacteria and enriched with metal(loid)-tolerant genera, including Pseudomonas, Flavobacterium, Novosphingobium, Pelosinus, and Thiothrix. These taxa are commonly associated with metal-contaminated environments and are known to employ diverse resistance strategies, such as metal efflux, enzymatic detoxification, biosorption to cell surfaces, extracellular polymeric substance production, oxidative stress mitigation, and metal(loid) reduction.
Cultivation-based methods yielded 70 bacterial isolates exhibiting substantial metal tolerance. Minimum inhibitory concentration assays demonstrated resistance to U (up to 8 mM) and multiple co-occurring metals, including Pb (up to 16 mM), Cu and Co (up to 4 mM), Zn (up to 8 mM), and Se (up to 32 mM). Selected strains, such as Curtobacterium flaccumfaciens, Paenibacillus amylolyticus, Allorhizobium sp., Commamonas jiangduensis, Chryseobacterium carnipullorum, and Herbaspirillum aquaticum displayed pronounced tolerance to Ba and Sr in growth experiments and showed measurable biosorption capacity, highlighting their adaptive potential in multi-metal environments. These findings advance current understanding of microbial adaptation to Ba- and Sr-enriched habitats and identify promising candidates for environmentally sustainable remediation strategies. Harnessing such microbial processes may improve the evaluation of contaminant mobility and bioavailability while supporting the development of green technologies for the restoration of metal(loid)-impacted ecosystems.
Acknowledgment. This work was supported by SURRI project GA No 101079345, provided by HORIZON Twinning in 2024 and the Student Grant Competition SGS-2024-3490.