Examination of the interaction of a halophilic Archaea with uranium regarding the long term storage of radioactive waste in rock salt

For the long term storage of radioactive waste in a deep geological repository rock salt is one of the possible host rocks, next to clay and crystalline formations. To date only little is known about the microbial diversity in German rock salt and the interactions of halophilic microorganisms with radionuclides. Microorganisms indigenous to potential host rocks are able to influence the oxidation state and speciation and hence the mobility of radionuclides. Therefore, for the safety assessment of a radioactive waste disposal it is important to know what microorganisms are present in the potential host rocks (e.g. salt) and how these microorganisms can affect the performance of a repository.
The reference organism Halobacterium noricense DSM 15987 was used to investigate the interactions with uranium at high ionic strength. For instance this halophilic Archaea was found in an Austrian salt mine1 and in the halite of the Waste Isolation Pilot Plant (WIPP, Carlsbad, USA)2. The cells were incubated for 48 h with uranium concentrations between 5 - 60 μM in 3.0 M NaCl (pH 6.0, room temperature, shaking) for sorption studies. After 48 h the cells were still living when incubated with uranium concentrations up to 60 μM, which demonstrates that Halobacterium noricense can tolerate uranium concentrations up to this level. The formed uranium sorption species were examined with IR-spectroscopy and time-resolved laser-induced fluorescence spectroscopy (TRLFS). Furthermore the time-depending and pH-depending biosorption of Halobacterium noricense with uranium will be presented.
1. Gruber, C.; Legat, A.; Pfaffenhuemer, M.; Radax, C.; Weidler, G.; Busse, H. J.; Stan-Lotter, H., Halobacterium noricense sp. nov., an archaeal isolate from a bore core of an alpine Permian salt deposit, classification of Halobacterium sp. NRC-1 as a strain of H. salinarum and emended description of H. salinarum. Extremophiles 2004, 8 (6), 431-439.
2. Swanson, J. S.; Reed, D. T.; Ams, D. A.; Norden, D.; Simmons, K. A., Status report on the microbial characterization of halite and groundwater samples from the WIPP. Los Alamos National Laboratory 2012.