Speciation of Se(IV) and Eu(III) associated with Stenotrophomonas bentonitica BII-R7 isolated from Spanish bentonites

Deep geological repositories (DGR) are designed to store radioactive wastes in the near future using artificial barriers like bentonites. These formations have been characterized by their high microbial diversity and activity [1]. Consequently, bentonite microbial populations would interact with radionuclides stored within DGR affecting their fate and behaviour. This study is focused on the elucidation of the mechanism involved in the interactions of Se(IV) and Eu(III) withthe bacterial strain Stenotrophomonas bentonitica BII-R7 under anaerobic and alkaline conditions using multidisciplinary approach combining microscopy, microbiology and spectroscopy. This strain was isolated from bentonites of Cabo de Gata (Almeria, Spain) [2]. The isolate BII-R7 is able to reduce Se(IV) to Se(0) under DGR relevant conditions forming Senanoparticles (Se NPs). Size, structure, morphology and cellular location of the Se NPswere analysed by STEM/HAADF, FESEM, UV-Vis spectroscopy, etc. In addition, flow cytometry studies were conducted to evaluatethe toxicity of Se(IV) on cell viability and metabolic activity.S. bentoniticais also able to interact with Eu(III) mainly by a biosorption process as indicated spectroscopic, microscopic and kinetic studies. Time-Resolved Laser-induced Fluorescence Spectroscopy (TRLFS) results also suggested that phosphoryl and carboxyl groups from the cells have an important role in the Eu(III) coordination sites.
[1] Lopez-Fernandez et al. (2014) Appl Geochem 49, 77-86.
[2] Sanchez-Castro et al. (2017) ) Int J Syst Evol Microbiol [in revision].