We say that a bit (too much), but plants aren't the only ones – nor were they the first – to harness the sun's energy to convert water and carbon dioxide into sugar and oxygen. Long before the emergence of the plant kingdom, bacteria carried out photosynthesis in the ocean.
Moreover, it was the absorption (and not digestion) of photosynthetic bacteria by a larger cell that gave birth to the first algae… and for this reason, moreover, “cyanobacteria” (blue-green bacteria) and cyanobacteria. The organelles (sections) of plant cells in which photosynthesis takes place, called chloroplasts, resemble two drops of water.
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Search for the first thylakoids
Cyanobacteria, and subsequently algae, have enriched our atmosphere with oxygen on several occasions in our planet's history, which likely contributed to the evolution of certain forms of life – including the ancestors of the creatures that inhabit the emerging seas and lands of today.
These “sister twins” that are cyanobacteria and plant chloroplasts contain membranes called “thylakoids”, rich in chlorophyll, the famous pigment that absorbs the wavelengths of red, yellow and violet (and returns the blue color to our eyes – green).
Therefore, whoever finds the first thylakoids will reveal one of the most important secrets of life on our planet… and the matter may be settled if a new study is 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) dating back at least 1.75 billion years, researchers discovered a fossil microbe of this type. Navifosa magenensis 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 existence of metabolically active cyanobacteria that perform oxygenic photosynthesis.”write the four scientists from the University of Liège (Belgium).
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Significant oxidation
If the oldest cyanobacterial fossil dates back to just over 2 billion years ago, it does not appear to have thylakoid membranes, unlike the new fossil, our colleagues detail from Science Alert.
The authors suggest that analyzing other rocks using the sophisticated techniques their team uses will help detect such membranes in older fossils. Perhaps it is enough to be able to confirm that photosynthetic organisms did indeed cause the “major oxidation” of the atmosphere 2.4 billion years ago…
On the same topic
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