A new discovery by an international team of researchers may have shed light on a long-standing question in biology: which came first, oxygen production through photosynthesis or oxygen consumption through aerobic metabolism? According to a study published in the Proceedings of the National Academy of Sciences, scientists have identified a possible missing link molecule that could provide an answer.
The study’s lead author, Felix Elling, was working on a project unrelated to this question when he stumbled upon a unique variation of a quinone molecule found in nitrogen-utilizing bacteria. Quinones are essential molecules that occur in all life forms and have two primary types: aerobic quinones that require oxygen and anaerobic ones that do not.
The researchers discovered methyl-plastoquinone, a third type of quinone that is similar to what plants use for photosynthesis. This finding suggests that there may be a missing link between the two types of quinones, providing insight into the evolutionary history of aerobic metabolism.
The study’s findings have implications for our understanding of the Great Oxidation Event, which marked the transition from anaerobic to aerobic life forms around 2.3 billion years ago. While it has long been assumed that photosynthesis came first, the discovery of methyl-plastoquinone supports an alternative hypothesis: some bacteria may have already had the ability to utilize oxygen before cyanobacteria began producing it.
“This is a major breakthrough,” said Ann Pearson, a professor at Harvard University who collaborated with Elling on the study. “The discovery of this molecule sheds light on how life adapted to its environment and paved the way for the diversification of life as we know it today.”
The researchers believe that methyl-plastoquinone may be the primary or ancestral form of quinones, which were later adapted into different forms in plants and animals. This finding provides a unique window into the evolutionary history of oxygen consumption and has significant implications for our understanding of the origins of life on Earth.
Source: https://phys.org/news/2025-02-accidental-discovery-hint-chicken-egg.html