Oldest evidence of photosynthesis found in 1.75 billion-year-old microfossils

(CN) — Scientists have discovered the oldest evidence of photosynthetic structures inside 1.75 billion-year-old microfossils, found in rock samples in Australia.

"With this discovery, we can identify the fossil as a sign of bacteria, that's performing oxygenic photosynthesis," said Emmanuelle Javaux, a professor of astrobiology at the University of Liège in Belgium, and one of the co-authors of the paper, published Wednesday in the journal Nature. "And it's kind of a big deal to be able to identify fossils based on this. Because cyanobacteria are very important bacteria for the evolution of our planet and for life."

The cyanobacteria are a phylum of bacteria containing thylakoid membranes, which convert light into energy. Scientists discovered traces of them inside the microfossil known as "Navifusa majensis," which researchers describe in their paper as "an enigmatic, ellipsoidal, organic-walled microfossil," the "taxonomic identity" of which remains "unresolved."

To obtain the samples of microfossils, the team of scientists took rock samples from five different spots on Earth, including Canada and the Democratic Republic of the Congo. The samples were cleaned and crushed, then bathed in different acids. Researchers then took the tiny samples and sliced into ultrathin sections, which were then studied with a powerful electron microscope.

Of great interest to Javaux and other scientists is determining whether or not photosynthesis evolved before or after the Great Oxidation Event, a period of time around 2.4 billion years ago when levels of oxygen in the Earth's ocean and atmosphere began rising precipitously.

Regardless, we know that cyanobacteria played an integral role in the development of life on Earth.

"If we are interested in the early version of our planet and life, these cyanobacteria are very important microorganisms, because they are the one who invented this oxygenic photosynthesis," said Javaux. "This changed, completely, the chemistry of Earth over the years. And in fact, without oxygen, you would not have eukaryotes" — that is, organisms with cells containing a membrane-bound nucleus — "so you would not have us. We are but a tiny branch in the tree of eukaryotes."

Follow @hillelaron

Subscribe to Closing Arguments

Sign up for new weekly newsletter Closing Arguments to get the latest about ongoing trials, major litigation and hot cases and rulings in courthouses around the U.S. and the world.

Email *

Submit