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Dr. Johannes Raff

Head Biogeochemistry
j.raffAthzdr.de
Phone: +49 351 260 2951

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Department of Biogeochemistry

Research in the Biogeochemistry department focuses on understanding the interaction of long-lived radionuclides with biosystems. We are interested in the various levels from biomolecules to individual organisms and complex biocoenoses. On the one hand, the aim is to understand the influence of biological systems on the behavior of radionuclides in the environment (release, mobility and bioavailability). On the other hand, we investigate the effects of radionuclides on the metabolism of cells and the whole organism (uptake, accumulation, chemo- and radiotoxicity) and the resulting dangers for us humans.

Using state-of-the-art molecular biological, spectroscopic and microscopic methods, we work in the fields of repository research to improve the long-term safety of a repository for high-level radioactive waste and radioecology to protect humans and the environment from the dangers of naturally and artificially released radionuclides.

In addition to basic research, our aim is to use the knowledge gained to develop innovative remediation methods and improve models to describe the behavior of radionuclides in the environment.

Interested in working with us?

To support our work, we are always looking for students and interns from the fields of biology, chemistry and environmental sciences who either want to write their thesis with us or simply gain practical experience. Are you interested? Then please get in touch to clarify any questions you may have.

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

Investigating the interaction of uranium(VI) with diatoms and their bacterial community: A microscopic and spectroscopic study

He, Y.; Wei, T.-S.; Kluge, S.; Flemming, K.; Sushko, V.; Hübner, R.; Steudtner, R.; Raff, J.; Mallet, C.; Beauger, A.; Breton, V.; Péron, O.; Stumpf, T.; Sachs, S.; Montavon, G.

Abstract

Diatoms and bacteria play a vital role in investigating the ecological effects of heavy metals in the environment. Despite separate studies on metal interactions with diatoms and bacteria, there is a significant gap in research regarding heavy metal interactions within a diatom-bacterium system, which closely mirrors natural conditions. In this study, we aim to address this gap by examining the interaction of uranium(VI) (U(VI)) with Achnanthidium saprophilum freshwater diatoms and their natural bacterial community, primarily consisting of four successfully isolated bacterial strains (Acidovorax facilis, Agrobacterium fabrum, Brevundimonas mediterranea, and Pseudomonas peli) from the diatom culture. Uranium (U) bio-association experiments were performed both on the xenic A. saprophilum culture and on the four bacterial isolates. Scanning electron microscopy and transmission electron microscopy coupled with spectrum imaging analysis based on energy-dispersive X-ray spectroscopy revealed a clear co-localization of U and phosphorus both on the surface and inside A. saprophilum diatoms and the associated bacterial cells. Time-resolved laser-induced fluorescence spectroscopy with parallel factor analysis identified similar U(VI) binding motifs both on A. saprophilum diatoms and the four bacterial isolates. This is the first work providing valuable microscopic and spectroscopic data on U localization and speciation within a diatom-bacterium system, demonstrating the contribution of the co-occurring bacteria to the overall interaction with U, a factor non-negligible for future modeling and assessment of radiological effects on living microorganisms.

Keywords: Achnanthidium saprophilum; 16S rRNA genes; Extracellular polymeric substance (EPS); Co-localization; Luminescence spectroscopy; Radionuclides; Uranium

Permalink: https://www.hzdr.de/publications/Publ-38772

More publications

Projects

An overview of completed projects can be found here.

Team

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

Head

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

Employees

NameBld./Office+49 351 260Email
Rahel Bertheau801/P3543138
Dr. Björn Drobot801/P3172895
b.drobotAthzdr.de
Katrin Flemming801/P3092958
k.flemmingAthzdr.de
Dr. Alix Günther801/P2562433
2522
a.guentherAthzdr.de
Max Klotzsche801/P3063241
m.klotzscheAthzdr.de
Dr. Evelyn Krawczyk-Bärsch801/P2522076
e.krawczyk-baerschAthzdr.de
Raul Eduardo Linares Jimenez801/P1032457
r.linares-jimenezAthzdr.de
Julia Marie Mätzkow801/P3062860
j.maetzkowAthzdr.de
Dr. Henry Moll801/P2562433
2549
h.mollAthzdr.de
Antonio Newman Portela801/P1032720
a.newman-portelaAthzdr.de
Dr. Susanne Sachs801/P2082436
s.sachsAthzdr.de
Jana Seibt801/P2193194
2510
j.seibtAthzdr.de
Dr. Robin Steudtner801/P3172895
r.steudtnerAthzdr.de
Lukas Waurick801/P3063241
l.waurickAthzdr.de
Toni Webert.weberAthzdr.de

MICRONUC

NameBld./Office+49 351 260Email
Dr. Andrea Cherkouk801/P3562989
a.cherkoukAthzdr.de
Sindy Kluge801/P2193194
s.klugeAthzdr.de
Dr. Nicole Matschiavelli801/P3182759
n.matschiavelliAthzdr.de
Dr. Ting-Shyang Wei801/P3182759
t.weiAthzdr.de