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The oldest photosynthetic organisms known to biology are cyanobacteria that evolved billions of years ago. Commonly referred to as blue-green algae, they are still at work producing oxygen as a byproduct of harvesting the Sun’s radiation. Because oxygen has been present in Earth’s atmosphere in significant quantities since 2.4 billion years ago (in an event called the Great Oxidation Event), it is assumed that cyanobacteria, or some evolutionary predecessor, has existed for at least this long. However, there has been debate among scientists regarding when the photosynthetic structures present in current cyanobacteria may have evolved. These structures are called thylakoid membranes, and they form stacks within the bacteria that efficiently harvest the Sun’s light and pump out oxygen.
A new study has analyzed fossil cyanobacteria present in Australian shale dated to between 1.73 and 1.78 billion years ago, and reports evidence for the presence of thylakoid membranes (see the figure above). This is the earliest evidence of such structures in cyanobacteria, 1.2 billion years older than any previous evidence.
“We didn’t know that they could be preserved in such old microfossils,” [astrobiologist Emmanuelle Javaux] says. But she has no doubt that the dark lines stacked through tiny sausage-shaped cells represent thylakoids. “It cannot be something else, actually. This arrangement is very unique to cyanobacteria with thylakoids,” she says.
The fossil bacteria had been laid down in mud and squeezed as the mud was transformed into shale over time, yet the internal structures of the cells were preserved.
“It suggests this kind of future where we might be able to pull more information, more cell biology and morphological detail out of these minuscule fossils,” [geobiologist Woodward Fisher] says.
Good fossil specimens of this age are rare, but perhaps if even older high-quality specimens are found, it will be possible to determine when cyanobacteria acquired thylakoid membrane stacks.
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From inkstainedwretch:
Tamar’s comment in marcorfanos’ recommended diary about the murder of their son in a mass shooting. Good understanding of how massively uncivilized our American civilization is with regard to guns.
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This comment by jjd1983d in Blue Tuesday’s recommended diary on Chris Rufo’s fraudulent Harvard degree.
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