Opalinus Clay-associated microbial communities
Clay rocks are being considered to serve as host rock for the final disposal of high-level nuclear waste in a deep geological repository. Properties such as a high swelling capacity and a low water activity are favourable to suppress microbial activity. However, excavation and perturbation of the host rock can provide increased space, water and substrates for microbial life and activity. Little is known about the impact of microorganisms on the long-term safety of geological repositories. Thus, a more complete understanding of microbial community structure and function in these deep subsurface environments is needed to provide important information to evaluate the safety of a geological repository for radioactive waste in clay rocks.  In order to understand the autochthonous microbial communities and their potential to affect the repository's integrity, we analysed the microbial community composition (16S rRNA high-throughput sequencing) of Opalinus Clay rock and the adjacent Passwang formation from the Mont Terri underground research laboratory in Switzerland in the context of mineralogy and geochemistry.