Ph.D. projects

Interaction of halophilic microorganisms with radionuclides

Ph.D. student:
Miriam Bader
Prof. Dr. Thorsten Stumpf, Dr. Andrea Cherkouk (HZDR)

In Germany salt rock is, next to clay and crystalline formations, one of the three possible host rocks for the long term storage of radioactive waste in a deep geological repository. Despite the high salt concentrations some microorganisms are able to live under these extreme conditions. To date little is known about the diversity of halophilic microorganisms in German salt rock formations and their interaction with radionuclides. For the safety and stability of the nuclear waste repository it is important to know what kind of microorganisms are present and how they influence the performance of a repository.

The halophilic reference organism Halobacterium noricense DSM 15987, isolated from an Austrian salt mine1, will be used to study its interactions with radionuclides such as uranium and plutonium. This organism is also indigenous in the halite of the Waste Isolation Pilot Plant (WIPP, Carlsbad, USA)2. Halobacterium noricense is a halophilic Archaea, which prefers high salty conditions (optimum 3 M NaCl)1. The aim of this work is to characterize the reference organism (RFLP, microscopy, sequencing, potentiometric titration) and to investigate its interactions with uranium as e.g. biosorption behavior in batch experiments. Therefore, parameters will be varied, like uranium concentrations, pH value, temperature, dry biomass and sorption time. The formed uranium complexes will be investigated with TRLFS, IR-spectroscopy and XAS and their cellular localization will be examined with TEM/EDX.

  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.; Simmons, K. A.; Norden, D.; Ams, D. A.; Reed, D. T., Status report on the microbial characterization of halite and groundwater samples from the WIPP. Los Alamos National Laboratory 2012.