UP News - University of Potsdam

Photo: Thomas Roese

Dr. Sven Stripp and Max Klamke working at the anaerobic chamber.
Photo: Thomas Roese

Max Klamke prepares the infrared spectrometer.

How can microorganisms survive in extreme environments such as volcanic lakes or salt marshes? A giant metalloenzyme makes it possible: the heterodisulfide reductase super-assembly is found in microorganisms that produce methane from hydrogen and carbon dioxide. The super-assembly helps them adapt to changing habitats in the absence of oxygen. Using microscopic and spectroscopic methods, a team from the universities of Marburg and Potsdam succeeded in deciphering the role of the metalloenzyme in methane production. Their findings were published in the journal “Nature”.

Anaerobic microorganisms live under extreme conditions: high salt concentrations, extreme temperatures, and no oxygen. Such habitats are found not only in volcanic lakes or underground sediments, but also in the salt marshes along the German North Sea coast. There, methanogenic archaea use hydrogen (H₂) or formic acid as an electron source to reduce carbon dioxide (CO₂) to methane (CH₄). Methane is a potent greenhouse gas and contributes significantly to global warming. For this reason, understanding biological CH₄ production – methanogenesis – is particularly important for research into global carbon cycles.

A team from the universities of Marburg and Potsdam has now characterized one of the largest metalloenzymes known to date: the heterodisulfide reductase super-assembly. This molecular machine has a diameter of about 50 nanometers, making it roughly the size of a virus. The assembly comprises more than 250 protein molecules and over 600 metal compounds (“cofactors”). It links the first and last steps of methanogenesis – that is, the reduction of CO₂ and the regeneration of heterodisulfide, a sulfur compound produced during CH₄ production that is important for the energy metabolism of microorganisms. The large number of protein molecules and the spatial arrangement of the metal cofactors enable efficient electron transfer, allowing many reactions to proceed simultaneously.

Using cryogenic electron microscopy and infrared spectroscopy, the team deciphered the structure of the assembly and demonstrated the functional coupling of the protein molecules. “We have observed that CO₂ reduction occurs exclusively in the presence of H₂ and heterodisulfide,” emphasizes Max Klamke, Phd student in the group of Dr. Sven Stripp at the University of Potsdam. In addition to analyzing isolated complexes, Prof. Jan Schuller’s research group studied the enzymes using cryogenic electron tomography. “These data show that the super-complexes are present in high density within the cells and presumably play a central role in electron flow and energy storage during methanogenesis,” explains Sophia Paul, PhD student in the working group of Prof. Jan Schuller at the University of Marburg.

Link to Publication: https://doi.org/10.1038/s41586-026-10744-9

Weitere Informationen zur Arbeitsgruppe von PD Dr. habil. Sven T. Stripp: https://www.uni-potsdam.de/de/specbiocat/sven-t-stripp

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