PhD thesis

Influence of Biofilms on Migration of Uranium, Americium and Europium in the Environment

Pic Zirnstein

PhD student:
Isabel Zirnstein
Prof. Dr. I. Röske (TU Dresden), Prof. Dr. G. Bernhard, Dr. T. Arnold (HZDR)

Microorganisms often form communities, so-called biofilms, in its natural habitats. In every territory of the world they play an important role. Biofilms contain different types of microorganisms e.g. bacteria, fungi, amoebae, algae etc. Together with the self-produced matrix, called EPS (extracellular polymeric substances), they constitute a kind of microenvironment. Just the same way toxic heavy metals could possibly infiltrate the biofilm. In order to understand the migration and transport processes of uranium in nature it is necessary to study the interaction of uranium with biofilms.

In this study biofilms from different radionuclide-contaminated habitats will be analyzed, how biofilms can accumulate, bind or change radionuclides. That gives us information about mobilizing / immobilizing and transport processes of radionuclides in biofilms.

Methods will be used are listed in the following text:

  1. Determination of microbial (prokaryote and eukaryote) diversity from biofilms by light microscopy, fluorescence-in-situ-hybridisation and molecular methods (PCR, cloning, pyrosequencing).
  2. RNA-Analyses for determination which species of microorganisms are metabolic active. Staining of metabolic active/inactive microorganism of the biofilm.
  3. EPS (extracellular polymeric substances)-analyses by Maldi-TOF.
  4. Staining and Imaging of biofilms / EPS and the interactions with heavy metal and radionuclides by CLSM-LIFS (confocal laser scanning microscopy coupled with laser induced fluorescence spectroscopy).
  5. Visualizing of the biofilm with radionuclides in detail by TEM (Transmission electron microscopy).

Aim of the study is to characterize the whole biofilm. The focus is on the composition of species from biofilms in radioactive contaminated milieus. The study should explain which factors (cells, EPS) of the biofilms play a role at binding of heavy metals and radionuclides.