Dr. Johannes Raff

Head Biogeochemistry
Phone: +49 351 260 2951

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Department of Biogeochemistry


In the environment physical, chemical and biological processes influence the migration behavior of long-lived radionuclides (RN). In the biosphere mainly prokaryotic and eukaryotic microorganisms are involved in element cycles and the mobilization or immobilization of many radioactive and non-radioactive elements. Furthermore, their physiology and biochemistry are optimized to allow them to live and survive in almost all environments existing on earth even over long periods of time. Besides that, the interaction of radionuclides with microbes and higher organisms determine the fate of the radionuclides in nature and in the end their potential threat to human health. The aim of the research in the Department of Biogeochemistry is to identify dominating processes in the ecosphere including the food chain, to understand the biochemistry of the processes on a molecular level and to estimate their relevance for the radionuclide migration and transfer not only in nature but also in an engineered subsurface e.g. a deep-geological repository for radioactive waste. Beside the fundamental research it is also intended to generate thermodynamic data to improve the safety assessment modelling.

Current research topics

Working fields of the departement of biogeochemistry at the Institute of Resource Ecology (EN) ©Copyright: Dr. Matschiavelli, Nicole
  • Determination of the microbial diversity in water and soil environments contaminated with heavy metals and radionuclides as well as in different host rocks for potential radioactive waste disposals
  • Microbe-radionuclide-interactions with reference strains and isolates
  • Interaction of eukaryotic cells with radionuclides and lanthanides in particular with plants, fungi, sponges and algae
  • Investigation of the interaction of selected bioligands and model compounds with f-elements
  • Characterization of microbial processes affecting the conditions in deep geological repositories for radioactive waste (e.g. transformation of bentonite as barrier material)
  • Calculation and determination of the metal speciation relevant to the environment
  • Verification and validation of transport models
  • Characterization of particles in the environment relevant to the transport of radionuclides
  • Investigation of the transport processes of radionuclides by particles (including microbes) in natural water

Latest Publication

Uranium(VI) interactions with Pseudomonas sp. PS-0-L, V4-5-SB and T5-6-I

Kasko, J.; Li, X.; Müller, K.; Ge, Y.; Vettese, G. F.; Law, G. T. W.; Siitari-Kauppi, M.; Huittinen, N. M.; Raff, J.; Bomberg, M.; Herzig, M.

Pseudomonas sp. are indigenous inhabitants of ombrotrophic bogs which can survive in acidic, nutrient-poor environments with wide temperature fluctuations. Their interactions with contaminant radionuclides can influence radionuclide biogeochemistry in boreal environment. Here, uranium (U(VI)) bioassociation by Pseudomonas sp. PS-0-L, V4-5-SB and T5-6-I isolated from a boreal bog was studied by a combination of batch contact experiments, spectroscopy and microscopy. All strains removed U from the solution and the U bioassociation efficiency was affected by the nutrient source, incubation temperature, time and pH. Highest U bioassociation occurred in the strains PS-0-L (0.199 mg U/gBDW) and V4-5-SB (0.223 mg U/gBDW). Based on in-situ attenuated total reflection Fourier transformation infrared spectroscopy (ATR FT-IR) analyses, the most likely functional groups responsible for U binding were the cell surface carboxyl groups. In addition, transmission electron microscopy with energy dispersive X-ray spectroscopy (TEM/EDX) showed dense intra-cellular round- and needle-like U accumulations in the cytoplasm and near to the inner cell membrane. The presence of U with phosphorus was indicated in elemental mapping. Modelled data showed ≡SOOHx-1 and ≡SOCO2Hx-1 as the dominant surface sites, contributing to the negative cell surface charge. The U removal efficiency depended on the U(VI) speciation under different pH conditions. At pH 5, the main species reacting with bacterial cell surfaces was UO22+, while at pH 9 UO2(OH)2 and UO2(OH)3- dominated the reactions. Further, U bioassociation increased with increasing aqueous U(VI) concentrations. Our data suggests U bioassociation on 1) outer cell membrane/cell wall associated carboxyl groups (e.g., proteins), and 2) intracellular phosphate groups (e.g., phospholipids).

Keywords: bioassociation; biosorption; bioaccumulation; modelling; carboxyl group; phosphate group

Experimental methods

  • Spectroscopy: LIFS (TRLFS, LIPAS); continuous wave fluorescence spectroscopy, UV-vis-NIR, XAS, Raman, ATR-FT-IR, NMR
  • Molecular biology (DNA extraction, PCR, Sanger sequencing, Next Generation Sequencing, heterologous expression of proteins)
  • Aerobic and anaerobic lab-scale cultivation of microorganisms in bioreactors (1-50 L)
  • Plant cell cultivation
  • Cell disruption in small and large volumes (mixer mill, ultra-sonic disruption, bead ruptor, high pressure homogenizer)
  • Microscopy: CLSM, REM, TEM, AFM, light and fluorescence microscopy
  • Chromatography: HPLC, FPLC
  • Protein biochemistry (isolation and characterization)


  • MIND, EU project, grant agreement No 661880, duration 01.06.2015 – 31.05.2019
  • BioVeStRa, BMBF support code 02S9276A, duration 01.06.2016-31.05.2019
  • CONCERT: European Joint Programme for the Integration of Radiation Protection Research; EC-Project grant agreement No 662287, duration 2015 -2020
  • TransAqua, BMBF support code 02NUK030F, duration 01.06.2013-30.11.2017
  • UMB project, BMWI support code 02E11344B, duration 01.04.2015-31.12.2017
  • BioNEWS, BMBF support code 03WKCL03F, duration 01.01.2015-31.12.2017
  • TRANS-LARA, BMBF support code 02NUK051B, duration 01.09.2017-28.02.2021
  • iCROSS, HGF/BMBF support codes SO-093 and 02NUK053B, duration 01.07.2018-30.06.2021
  • RadoNorm: Towards effective radiation protection based on improved scientific evidence and social considerations - focus on radon and NORM; EC Project, grant agreement No. 900009, 01.09.2020-31.08.2025
  • EURAD-MAGIC – NEA/EU-Projekt, duration 01.06.2019-31.05.2024
  • Ultrasens (WIPANO), BMWi support code 03THWSN004, duration 01.07.2020-31.10.2021
  • UMB II, BMWi support code 02E11870B, duration 01.01.2021-31.12.2023
  • EURAD-ConCorD – NEA/EU project, duration 01.06.2021-31.05.2024
  • RENA/ BMBF support code 02NUK066A, duration 01.09.2021-31.08.2024
  • PepTight/BMBFsupport code 031B1122A, duration 01.09.2021-31.08.2024
  • TRAVARIS/BMBF Projekt, Förderkennzeichen 15S9437C, Laufzeit 01.11.2022-31.10.2025


Foto: Gruppenbild der Abteilung Biogeochemie des Instituts für Ressourcenökologie ©Copyright: Dr. Johannes Raff


NameBld./Office+49 351 260Email
Dr. Johannes Raff801/P3142951


NameBld./Office+49 351 260Email
Dr. Björn Drobot801/P3172895
Katrin Flemming801/P3092958
Dr. Alix Günther801/P2562433
Max Klotzsche801/P3063241
Dr. Evelyn Krawczyk-Bärsch801/P2522076
Raul Eduardo Linares Jimenez801/P2052438
Dr. Henry Moll801/P2562433
Dr. Susanne Sachs801/P2082436
Jana Seibt801/P2193194
Dr. Robin Steudtner801/P3172895


NameBld./Office+49 351 260Email
Dr. Andrea Cherkouk801/P3562989
Dr. Ting-Shyang Wei801/P3182860