Microorganisms in potential host rocks for geological disposal of nuclear waste and their interactions with uranium

The long-term safety of nuclear waste in a deep geological repository is an important issue in our society. For the safety assessment of such a repository it is necessary to know what microorganisms are present in the potential host rocks (e.g. clay, salt) and how these microorganisms can influence the performance of a repository to potentially reduce their activity.
In this study, the analysis of bacterial diversity in a sample from the Mont Terri Opalinus clay demonstrated the predominance of representatives of Firmicutes, Betaproteobacteria, and Bacteriodetes. Alpha-, Beta- and Gammaproteobacteria were detected in the porewater samples from the Mont Terri rock laboratory, whereas Gammaproteobacteria especially Pseudomonas sp. dominated the bacterial community.
Among other isolates, a Paenibacillus sp., as a representative of Firmicutes, was isolated from the clay under anaerobic conditions. Accumulation experiments and potentiometric titrations showed a strong interaction of Paenibacillus sp. cells with U(VI) within a broad pH range (3-7) [1].
Additionally, we will present a study on the interactions of the halophilic archaea Halobacterium noricense DSM 15987, an salt rock representative reference strain, with U(VI) at high ionic strength. These results contribute to the safety assessment of a prospective nuclear waste repository.