The traces of one of the first bacteria to land on land, over 400 million years ago, have been discovered in some fossils found in Scotland: it is a cyanobacterium, that is, a microorganism capable of carrying out photosynthesis, which around that era expanded from aquatic to terrestrial environments, finding itself cohabiting with some of the first plants.
The discovery, published in the journal iScience, is due to a group of researchers led by the National Museum of Natural History in Paris, who reconstructed in 3D the fossil traces of the bacterium called Langiella scourfieldii, found in the so-called ‘Rhynie flint’: a deposit near the Scottish village of Rhynie famous for containing exceptionally preserved fossils of some of the earliest known terrestrial life forms.
Artistic reconstruction of the habitat of the Langiella scourfieldii bacteria (source: Viktor Leskyk, iScience, 2023)
Also known incorrectly as blue-green algae, cyanobacteria are crucial to life as we know it today: around 2.4 billion years ago they played a key role in transforming the Earth into a hospitable environment, pumping oxygen into the air and extracting CO2. They are in fact responsible for what is known as the Great Oxidative Event or Oxygen Catastrophe: a great mass extinction of primitive life forms that were instead adapted to living in a world with little oxygen.
It is assumed that these microorganisms ‘jumped’ from water to land quite quickly and easily, but the study led by Christine Strullu-Derrien constitutes an important piece of the puzzle that allows us to better understand how they managed to carve out a place for themselves, then continue to thrive to this day. “At that time, cyanobacteria played the same role as they do today,” says Strullu-Derien. “Some organisms use them as food, but they are also important for photosynthesis. We learned – adds the researcher – that they were already present when plants began to colonize the earth and may even have competed with them for space”.
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