Chlorophyll remnants preserved in the cells of a one-billion-year-old fossilized algae

(ORDO NEWS) — The geological record of the history of the Earth describes in detail a little more than half a billion years of the development of life. However, the more ancient stages of the formation of the biosphere (we are talking primarily about the Proterozoic era) are much more difficult to study.

During this time, organisms turn out to be too much destroyed, which, moreover, during life were often very fragile and had a microscopic size.

Scientists know that in the Proterozoic our planet was already inhabited, but the details of evolution at this stage can only be guessed at. Calculations by bioinformaticians showed that the main groups of organisms arose as early as the Proterozoic, but it was not easy to confirm this with reliable paleontological finds.

What’s more, the nature of many Proterozoic fossils remains in question—sometimes paleontologists aren’t even sure if they ‘re dealing with bacteria, multicellular algae, or animals.

A new article in Nature Communication is an example of a new approach to studying Proterozoic era specimens. An international team of scientists led by Marie Catherine Sforna from the Laboratory of Early Traces of Life and Evolution at the University of Liege (Belgium) for the first time managed to extract the remains of the chlorophyll molecule directly from the cells of the organism Arctic Cellular tetragonal.

This fossil was found in the Democratic Republic of the Congo and is estimated to be 1 billion years old. “We were able to find the breakdown products of chlorophyll, which suggests that Arctacellularia tetragonala was a phototrophic eukaryotic organism, one of the most ancient multicellular algae, the nature of which is beyond doubt,” says Marie Catherine.

In order to notice traces of chlorophyll, scientists had to use sophisticated physical methods based on fluorescence and synchrotron X-ray absorption. Recall: chlorophylls are a whole group of pigments, brightly colored substances. They are necessary for phototrophic organisms (be it higher plants, algae or some bacteria) in order to use the energy of sunlight and synthesize organic compounds.

The decay products of chlorophyll contained in ancient rocks, which retained a structural similarity with this photosynthetic pigment, are called geo porphyrins. It is noteworthy that scientists have found ancient geo porphyrins before.

However, in this case, these compounds are located directly inside the once living tissues of the multicellular organism Arctic Cellular tetragonal . This is what allows us to confidently attribute it to multicellular algae – eukaryotic organisms that have a cell nucleus. It turns out that Arctan Cellularia tetragonal is one of the oldest known algae.

This amazing discovery allows us to reconstruct the course of evolution that took place long before the emergence of most modern life forms. Moreover, it sheds light on changing conditions on ancient Earth and their causes.

After all, it was phototrophs (first bacteria, and later also eukaryotes) that caused radical transformations in the appearance of the Earth in the Proterozoic. The fact is that, as a by-product of photosynthesis, they, as a rule, release oxygen. The accumulation of this gas has changed the face of our planet beyond recognition and, in particular, made possible the emergence of a protective ozone layer.

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