It is not an exaggeration to say that one of the most important moments of evolution after the emergence of life was the creation of the process of photosynthesis, as the process of producing sugar and oxygen from water and carbon dioxide using the energy of light is the reason for the existence of trees, birds, people, and breathable air.
Based on geohistorical data, the increase in the level of oxygen in the atmosphere began 2.4 billion years ago, while the beginnings of photosynthesis can be traced back to 3 billion years ago. It is assumed that cyanobacteria first appeared independently and then inside plant cells, but we do not have any remains from this era. Therefore, it is important for researchers at the University of Liège nature The journal provides the oldest direct evidence known today.
The key to discovery is identifying what is called the thylakoid membrane. This is one of the major structural elements of earlier photosynthetic bacteria, a tightly coiled membrane that doubles the surface area per given volume. A large surface area is important so that as many photosynthetic proteins as possible can bind to it. In very thin slices of ancient rock, researchers have discovered
They were able to identify traces of the structure at the nanoscale using electron microscopy.
One of these fossils was found in rocks of the McDermott Formation in Australia, and the other in rocks of the Grassy Bay Formation in the Canadian Arctic. The latter is more than a billion years old, but the age of the McDermott rocks is estimated at 1.75 billion years.
The oldest remains of cyanobacteria are two billion years old, but their internal structure cannot be clearly determined. On the other hand, their role in the emergence of atmospheric oxygen cannot be proven, because they were formed after nearly half a billion years.
The importance of this discovery stems from the fact that the oldest remains of cyanobacteria do not contain thylakoid membranes, just as some species of cyanobacteria living today do not. The membrane is almost certainly the result of an evolutionary branching, during which a new species of efficient cyanobacteria moved to algae.
There is still no direct evidence as to whether this was the cause of the major oxygenation event that transformed the planet's atmosphere. But the 1.75 billion-year-old remains are the oldest known examples of thylakoid membranes, so they are a billion years closer to the oxygenation event, and later findings will likely prove they played an important role in the story.