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Scientists have discovered the earliest photosynthetic structures that could shed light on Earth’s primordial life and how the intricate process of photosynthesis evolved, Gizmodo reported.
Photosynthesis is the process in which plants – and some other lifeforms – convert sunlight into chemical energy.
In their paper, biologist Emmanuelle Javaux and her team discovered microfossils of Navifusa majensis, a presumed cyanobacteria, in northern Australia.
Cyanobacteria are a type of microorganism that get energy via oxygenic photosynthesis by converting water and carbon dioxide into glucose and oxygen using sunlight. They are also possibly the ancestors of plant chloroplasts, making their fossils crucial for unraveling the origins of photosynthesis.
The team identified microstructures in N. majensis known as thylakoids, a kind of membrane-bound structure found in plant chloroplasts and some modern cyanobacteria. This led to the conclusion that cyanobacteria with thylakoids split from those without occurred almost two billion years ago.
“This discovery extends the fossil record of such internal membranes by at least 1.2 billion years,” said Javaux. “The arrangement of these membranes in fossil cells allows their unambiguous identification as cyanobacteria actively performing early oxygenic photosynthesis at the time of death 1.75 billion years ago!”
The researchers explained that findings could help them understand how one of Earth’s most fundamental life processes emerged.
More than two billion years ago, Earth underwent the Great Oxidation Event that saw a significant increase in oxygen production. However, it’s unclear when the exact timing of oxygenic photosynthesis evolution in cyanobacteria occurred.
While this discovery adds another piece to the timeline of oxygenic photosynthesis, it does not provide clarity on when this process evolved in relation to the Great Oxidation Event. Further discoveries of fossils with thylakoids may contribute to answering this question.