In a quiet lab at the University of Liège, Louise Hambücken pored over the genetic blueprints of ancient microbes, tracing a story that began over 2.4 billion years ago—one that transformed Earth from a lifeless rock into a breathing, thriving planet. At the heart of this transformation: tiny internal membranes called thylakoids, the solar panels of life, where oxygen-producing photosynthesis first became possible. Now, for the first time, scientists have uncovered how these vital structures may have evolved in cyanobacteria, the pioneering organisms that set the stage for all complex life.
Thylakoids are where sunlight is converted into life-sustaining energy, releasing oxygen as a byproduct. Their emergence is considered one of the most pivotal events in evolutionary history—possibly triggering the Great Oxygenation Event that filled Earth’s atmosphere with oxygen. But how did these specialized membranes arise from simpler ancestors that performed photosynthesis at their outer skin, the plasma membrane? Fossils from that era are nonexistent, so Hambücken and her team turned to modern descendants: the rare Gloeobacterales, a group of cyanobacteria that still carry out photosynthesis without thylakoids.
By comparing the genomes of 170 cyanobacterial strains—some with thylakoids, some without—the team identified key proteins uniquely associated with thylakoid formation. These proteins, absent in Gloeobacterales, likely played a role in shaping the internal membrane systems that boosted photosynthetic efficiency. The study also revealed that while Gloeobacterales possess a simplified version of photosystem II, they lack several assembly factors essential for building the full complex—clues that point to a stepwise evolution of this life-changing machinery.
The implications stretch beyond understanding ancient biology. By decoding the minimal genetic toolkit needed to build photosynthetic membranes, scientists edge closer to engineering synthetic photosynthesis or enhancing crop efficiency. While still in the realm of fundamental science, this research lays the foundation for future biotechnologies that could harness sunlight more effectively, much like nature did billions of years ago.
"This is the first study to investigate the evolutionary processes underlying thylakoid formation through such an approach," says Hambücken. As we trace the origins of oxygen, we’re not just uncovering the past—we’re learning how life reshaped a planet, and how we might one day do the same.