Microbial Energy Conversion and Biotechnology

Prof. Dr. Jörg Simon

Publications (tu-biblio)
Literature is available upon request.
Press release, TU aktuell

Research Interests

Molecular microbiology and bioenergetics of the nitrogen cycle

The biogeochemical nitrogen cycle depends on a diverse range of microorganisms that catalyze key reactions like nitrogen fixation, nitrification, anaerobic ammonia oxidation (anammox), denitrification, as well as assimilatory and respiratory nitrate and nitrite ammonification.

We study the nitrogen metabolism of Epsilonproteobacteria, a phylogenetic group that comprises host-associated bacteria (e.g. pathogenic Campylobacter and Helicobacter species) as well as free-living terrestrial and aquatic bacteria that appear to be abundant in sulphidic environments like deep-sea vents.

Our work focuses on the enzymology and bioenergetics of anaerobic nitrate, nitrite and nitrous oxide respiration as well as nitrosative stress defence using the non-pathogenic bacterium Wolinella succinogenes as model Epsilonproteobacterium. This organism is genetically tractable and produces metalloprotein complexes that are part of electron transport chains in amounts sufficiently high for biochemical characterization and structure determination.

The mechanistic basis of anaerobic respiration with nitrogen compounds is elucidated using genetic manipulation (mutant construction, site-directed mutagenesis, overproduction of affinity-tagged proteins) as well as methods of molecular and structural biology.

Electron micrograph of a W. succinogenes cell and substrate conversions catalysed by respiratory enzymes involved in nitrate ammonification and nitrous oxide respiration as well as in nitric oxide and hydroxylamine detoxification. Dehydrogenases (yellow) and reductases (red) are connected via the menaquinone/menaquinol pool and contribute to the generation of a proton motive force (pmf) that drives ATP synthesis. The inset illustrates purification (heme stain) of a multiheme cytochrome c from Campylobacter jejuni that was overproduced in W. succinogenes. Hyd, Hydrogenase; Fdh, Formate dehydrogenase; Nap, periplasmic nitrate reductase; Nrf, cytochrome c nitrite reductase; Nos, nitrous oxide reductase.
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Substrate conversions of a W. succinogenes cell – for more information please click on the picture

Research topics at a glance:

  • Composition and bioenergetics of epsilonproteobacterialelectron transport systems involved in anaerobic respiration with nitrate, nitrite, nitric oxide, nitrous oxide, fumarate, polysulfide, sulphite and arsenate.
  • Structure and function of quinone / quinol-reactive membrane-bound proteins and multiheme cytochromes c.
  • Modular design of synthetic microbial electron transport systems. This project aims at rational energy metabolism design in biotechnological applications (Research focus: Synthetic Biology).
  • Stress responses of Epsilonproteobacteria to combat oxidative, peroxidative and nitrosative stress and underlying regulatory networks (Research focus: Biology of Stress Response).
  • Structure, function and specificity of bacterial membrane-bound cytochrome c synthases involved in cytochrome c biogenesis.

Open Positions

We are seeking highly motivated students at the BSc, MSc and PhD level. Projects for Bachelor and Master theses for students from Biology and Biomolecular Engineering are offered in the research areas described above. Please contact Jörg Simon for details on current projects.