Comparative analysis of uranium bioassociation with halophilic bacteria and archaea

Abstract

<div><p>Rock salt represents a potential host rock formation for the final disposal of radioactive waste. The interactions between indigenous microorganisms and radionuclides, e.g. uranium, need to be investigated to better predict the influence of microorganisms on the safety assessment of the repository. Hence, the association process of uranium with two microorganisms isolated from rock salt was comparatively studied. <i>Brachybacterium</i> sp. G1, which was isolated from the German salt dome Gorleben, and <i>Halobacterium noricense</i> DSM15987<sup>T</sup>, were selected as examples of a moderately halophilic bacterium and an extremely halophilic archaeon, respectively. The microorganisms exhibited completely different association behaviors with uranium. While a pure biosorption process took place with <i>Brachybacterium</i> sp. G1 cells, a multistage association process occurred with the archaeon. In addition to batch experiments, <i>in situ</i> attenuated total reflection Fourier-transform infrared spectroscopy was applied to characterize the U(VI) interaction process. Biosorption was identified as the dominating process for <i>Brachybacterium</i> sp. G1 with this method. Carboxylic functionalities are the dominant interacting groups for the bacterium, whereas phosphoryl groups are also involved in U(VI) association by the archaeon <i>H</i>. <i>noricense</i>.</p></div>