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Fossils of the cyanobacteria Navifusa majensis, found in Australia (1.78–1.73 billion years old) and Canada (1.01–0.9 billion years old), are the oldest photosynthetic bacteria discovered to date.
Scientists led by Catherine F. Demoulin from the University of Liège in Belgium examined the structure of these cyanobacteria using various microscopic techniques. Their research revealed the presence of a thylakoid membrane where photosynthesis takes place.
According to the researchers, who published their findings in the Nature journal in January this year, it was cyanobacteria that were among the first organisms to carry out oxygen-containing photosynthesis.
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Photosynthesis first began three and a half billion years ago, but did not produce oxygen. However, cyanobacteria with thylakoids could carry out so-called oxygenic photosynthesis, in which oxygen is produced. According to experts, this is said to have happened around 1.75 billion years ago.
Two billion years ago there was also a dramatic increase in oxygen levels in the atmosphere. However, it is not entirely clear whether it was the cyanobacteria that caused this increase. This period, known as the Great Oxygen Catastrophe, saw the first increase in the amount of oxygen in both the Earth’s atmosphere and the ocean.
Since oxygen was an unknown gas for many species, their extinction occurred. Although almost most living things on Earth died out, thanks to the oxygen in the Earth’s atmosphere, the ozone layer was formed and multicellular life forms emerged.
Based on the organisms discovered so far, we know that the oldest evidence of the existence of cyanobacteria is the species Eoentophysisalis belcherensis, which originated two billion years ago. However, scientists point out that some cyanobacteria do not have thylakoids and therefore cannot carry out photosynthesis.
The discovery of fossils of these cyanobacteria with thylakoids is indisputable evidence that oxygen-containing photosynthesis must have occurred on Earth as early as 1.75 billion years ago, reports the website Science Alert.
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“We hypothesize that similar ultrastructural analyzes of well-preserved microfossils could expand the geologic record of oxygenic photosynthesis and early, oxygen-poor ecosystems in which complex cells evolved,” the researchers write.
Why do we need photosynthesis?
Photosynthesis is the biochemical process in which solar energy is absorbed. This involves the conversion of H2O and CO2 from simple substances into more complex substances, but at the same time oxygen is also released. Photosynthesis is a necessary component of the complex processes in the Earth’s ecosystem, since thanks to it organic substances can be present in the biosphere. They are vital for the life of many organisms and humans.
There are two types of photosynthesis. While oxygen-containing photosynthesis produces oxygen, anoxygenic photosynthesis is characterized by the fact that no water enters this chemical reaction and therefore no oxygen is produced. Green plants, algae, cyanobacteria and some bacteria carry out photosynthesis.
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