VAAM Research Award
VAAM-Forschungspreis 2023 für Jan Schuller, Marburg
For his research on the biological carbon dioxide fixation of microorganisms, Dr Jan Schuller receives the 2023 Research Award of the Association for General and Applied Microbiology (VAAM). The Marburg microbiologist studies bacteria and their enzyme equipment. He clarified how enzymatic "nanowires" enable a surprisingly efficient conversion of CO2. He is thus laying the foundation for future biotechnological production of carbon compounds from atmospheric CO2. The VAAM will award the 10,000 euro prize for outstanding current work in the field of microbiology at its annual meeting in Göttingen on September 10, 2023.
How bacteria turn CO2 from the atmosphere into biofuels
A promising biological solution to reduce the high CO2 content in the atmosphere is the recycling of carbon with the help of acetogenic bacteria. These microorganisms can fix CO2 in large industrial plants - and produce biofuels and recycled carbon compounds from it. However, their metabolism is still a great mystery, which Schuller is working on researching.
Insights into biological structures of a cell by cryogenic electron microscopy: Molecular "wires" studded by enzymes (yellow) enable acetogenic bacteria to fix the greenhouse gas CO2 highly efficiently (blue: ribosomes, purple: cell envelope proteins). On the right, the wires are shown as a structural model. Figure: Sandra Schuller
The various - not necessarily related, but always living without oxygen - acetogenic bacteria use a special metabolic pathway. They produce acetate (acetic acid salt), which they use for respiration, like other living organisms use oxygen. This is probably the oldest biochemical metabolic pathway on Earth: from CO2 and hydrogen, which were already present on the early Earth, the bacteria form organic compounds, i.e. "living matter".
Schuller's group has begun to elucidate the individual enzymatic steps that are necessary for this. In the process, they characterised previously unknown mechanisms of the enzymes and their role in the metabolism of the bacteria.
One of these enzymes can use hydrogen directly to reduce CO2: This hydrogen-dependent CO2 reductase (HDCR) is 10,000 times more efficient than any chemical catalyst - making it a prime candidate for biotechnological research. To understand the molecular basis of this enzyme, Schuller's group studied it using cryo-electron microscopy. They revealed a surprising structure: the enzyme forms "nanowires" on which the enzymatic subunits are arranged. This unusual architecture explains the outstanding catalytic properties. The longer the "wire", the higher its activity. Mutation experiments show that long structures maximise the catalytic activity of the enzyme.
Cellular electron tomography provided insights into the natural environment of the wires: At the top of the cells sit large ring-shaped structures of intertwined "wires". "We suspect that this organisation is an adaptation to extreme environmental conditions," explains Schuller. It ensures a large surface area with many interconnected reaction centres for the oxidation of hydrogen. This means there are always enough electrons to capture and concentrate the CO2 diffusing into the cell. The HDCR thus enables an acetogenic carbon concentration mechanism, which is necessary to survive under harsh conditions.
Special tools are important for these studies: a protective gas tent, for example, ensures oxygen-free conditions for electron microscopic sample preparation. "The lifestyle of such microorganisms and their enzymes still hold many secrets," promises Schuller. "With our research, we want to contribute to solving societal problems such as man-made climate change by paving the way for the use of CO2 as a raw material for valuable products." Appropriately optimised microbes and novel synthetic metabolic pathways could reduce CO2 emissions and enable more sustainable production that integrates CO2 into the resource cycle.
In addition to Schuller's impressive list of publications, the VAAM highlights his broad spectrum of methods: structural biology, cryo-electron microscopy, single particle analysis, modelling, biochemical and cell biological principles for anaerobic investigations. "Schuller elucidated why HDCR outperforms all chemical catalysts developed to date," the jury praised. His expertise was rewarded last year with the highly endowed Starting Grant Two-CO2-One of the European Research Commission (ERC). For VAAM President Franz Narberhaus, Schuller is an exemplary committed researcher: "He is on fire for science - and shows courage and willingness to keep opening up new scientific fields and techniques".
Dr Jan Michael Schuller (36) is an Emmy Noether Junior Research Group Leader at the SYNMIKRO Research Centre and the Chemistry Department at the University of Marburg. He studied biochemistry at the University of Tübingen and received his doctorate in 2016 under Prof. Dr. Wolfgang Baumeister at TU München. This was followed by a postdoc with Prof. Dr. Elena Conti at the Max-Planck-Institute of Biochemistry in Martinsried. Schuller received the DFG's Heinz Maier-Leibnitz Prize in 2021 and an ERC Starting Grant in 2022 for his project Two-CO2-One.
Information: https://www.schullerlab.org
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