Chance discovery rewrites the history of breathing
Scientists have discovered a variant of a quinone molecule, methylplastoquinone. They were able to detect this in a nitrogen-utilizing bacterium (Nirtospirota) and show that the basics of oxygen respiration developed earlier than 2.3 billion years ago, long before there was oxygen in the atmosphere. The results, which were produced under the leadership of Kiel University (CAU), were published in the international journal Proceedings of the National Academy of Science (PNAS).
Dr. Felix Elling uses highly specialized methods to analyse samples. In the laboratory, the molecular structures are determined using high-performance liquid chromatography coupled with mass spectrometry.
Jürgen Haacks / Uni Kiel
No event in the history of the Earth has provided living organisms with as much energy as the development of oxygen respiration. It made it possible to efficiently convert food into energy. However, when and in which organisms this ability was developed and which process arose first: photosynthesis, which releases oxygen, or oxygen respiration, which uses it, is the subject of scientific debate. A chance discovery by an international team of researchers could now provide a decisive clue to the evolutionary sequence of these processes. Under the leadership of Kiel University, the scientists discovered a variant of a quinone molecule, methylplastoquinone. They were able to detect this in a nitrogen-utilizing bacterium (Nirtospirota) and thus show that the basics of oxygen respiration developed earlier than 2.3 billion years ago, long before there was oxygen in the atmosphere.
Research team discovers new molecule variant
"We were studying bacteria for a completely different project when we observed an unusual change in a molecule of a nitrogen-utilizing bacterium," said the first author of the study, Dr. Felix Elling from the Leibniz Laboratory for Age Determination and Isotope Research at Kiel University, describing the accidental discovery. "We suspected from the outset that this could be a crucial building block related to the development of photosynthesis and the ability to breathe oxygen," continues Elling, who began his research at Harvard University (USA).
The international team of researchers, including researchers from the University of Bremen, the University of Grenoble (France) and the Massachusetts Institute of Technology (MIT, USA), discovered methylplastoquinone, a variant of a molecule called quinone. Until now, researchers assumed that there were only two different types of quinones, which are found in all living organisms and control metabolism: anaerobic quinones in bacteria, which do not breathe oxygen, and aerobic quinones, which are used by plants for photosynthesis and by humans, animals or bacteria for oxygen respiration. The researchers have now discovered a third type, methylplastoquinone, for the first time. This has the basic structure of aerobic quinones, but still has some characteristics of the anaerobic form. "Finding a quinone similar to the one that plants use for photosynthesis in a bacterium that breathes oxygen was very unusual. We realized that methyl plastoquinone could be a third type of quinone and may be the missing link between the two types of quinones," explains Felix Elling. The team only found the previously unknown molecule in bacteria of the phylum Nitrospirota, organisms that play a major role in the global nitrogen cycle.
Molecule existed earlier than 2.3 billion years ago
The results of the Kiel and international researchers also contribute significantly to a better understanding of a geological event, the so-called Great Oxygenation Event, which took place around 2.3 to 2.4 billion years ago. This event marks a turning point in the history of respiration, as cyanobacteria began to produce large amounts of oxygen through photosynthesis for the first time, thus enabling an aerobic metabolism. The existence of methylplastoquinone now disproves the hypothesis that photosynthesis came first. The molecule and its biosynthetic pathway are a decisive indication that some bacteria were already able to use oxygen before the cyanobacteria began to produce it.
In their work, the international research team was able to identify the original form of this molecule, which formed the basis for later adaptations - one for functions in algae and plants and another in the mitochondria in the human organism. "This molecule is a time capsule," summarizes Elling. "A living fossil of a molecule that has survived for more than two billion years."
Fundamentals of oxygen respiration laid down early on in bacteria
The foundations for oxygen respiration were therefore laid early on in the Earth's history. Later, around 2.5 billion years ago, when a lot of oxygen accumulated in the atmosphere, the ability to use oxygen for energy production developed from this. This evolutionary innovation of oxygen respiration was adopted by the eukaryotes. In the cells of eukaryotes, including humans, this evolutionary event has been passed down in the mitochondria, the power plants of our cells.
Note: This article has been translated using a computer system without human intervention. LUMITOS offers these automatic translations to present a wider range of current news. Since this article has been translated with automatic translation, it is possible that it contains errors in vocabulary, syntax or grammar. The original article in German can be found here.
Original publication
Felix J. Elling, Fabien Pierrel, Sophie-Carole Chobert, Sophie S. Abby, Thomas W. Evans, Arthur Reveillard, Ludovic Pelosi, Juliette Schnoebelen, Jordon D. Hemingway, et al.; "A novel quinone biosynthetic pathway illuminates the evolution of aerobic metabolism"; Proceedings of the National Academy of Sciences, Volume 122, 2025-2-20
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