2024-01-08 19:24:00
We say it (too) little, but plants are not the only ones – and were not the first – to exploit the sun’s energy to transform water and carbon dioxide into sugar and oxygen. Long before the advent of the plant kingdom, photosynthesis was carried out in the ocean by bacteria.
It was moreover the absorption of a photosynthetic bacteria (and the non-digestion of it) by a larger cell which gave birth to the first algae… which is why, moreover, the “cyanobacteria” ( blue-green bacteria) and the organelles (compartments) of plant cells where photosynthesis takes place, called “chloroplasts”, look like two drops of water.
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The quest for the first thylakoids
Cyanobacteria and then algae have enriched our atmosphere with oxygen on several occasions in the history of our planet, which has potentially favored the development of certain forms of life – including the ancestors of the beings who today populate the seas and the Emerged lands.
These “fraternal twins” that are cyanobacteria and plant chloroplasts contain membranes called “thylakoids”, rich in chlorophyll, the famous pigment which absorbs the wavelengths of red-yellow and violet (and returns blue to our eye -Green).
Therefore, whoever finds the first thylakoids will unlock one of the most important secrets of life on our planet… It may be a done deal, if a new study published in the journal Nature (January 3, 2024).
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Oldest evidence of photosynthesis?
By analyzing rock samples taken from the Australian desert (McDermott Formation) and dated at least 1.75 billion years ago, the authors discovered a fossil microbe of the species Navifusa majensis in which they identified what they believe to be thylakoid membranes. This would therefore be the oldest evidence of photosynthesis recorded on Earth.
“Our study provides direct evidence for the presence of metabolically active cyanobacteria performing oxygenic photosynthesis”write the four scientists from the University of Liège (Belgium).
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Great oxidation
If the oldest cyanobacteria fossil dates back a little over two billion years, it did not seem to contain thylakoid membranes, unlike the new fossil, detail our colleagues from Science Alert.
The authors suggest that analyzing other rocks using the cutting-edge techniques employed by their team will help spot such membranes in even older fossils. Enough, perhaps, to be able to confirm that photosynthetic organisms indeed triggered the “great oxidation” of the atmosphere 2.4 billion years ago…
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