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A stepping-stone for oxygen on Earth: Researchers find evidence of an early manganese-oxidizing photosystem

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Posted June 27, 2013
Caltech graduate student Jena Johnson examines a 2.415 billion-year-old rock in South Africa where evidence of an early manganese-oxidizing photosystem was found. Credit: Caltech

Caltech graduate student Jena Johnson examines a 2.415 billion-year-old rock in South Africa where evidence of an early manganese-oxidizing photosystem was found. Credit: Caltech

For most terrestrial life on Earth, oxygen is necessary for survival. But the planet’s atmosphere did not always contain this life-sustaining substance, and one of science’s greatest mysteries is how and when oxygenic photosynthesis—the process responsible for producing oxygen on Earth through the splitting of water molecules—first began. Now, a team led by geobiologists at the California Institute of Technology (Caltech) has found evidence of a precursor photosystem involving manganese that predates cyanobacteria, the first group of organisms to release oxygen into the environment via photosynthesis.

The findings, outlined in the June 24 early edition of the Proceedings of the National Academy of Sciences (PNAS), strongly support the idea that manganese oxidation—which, despite the name, is a chemical reaction that does not have to involve oxygen—provided an evolutionary stepping-stone for the development of water-oxidizing photosynthesis in cyanobacteria.

“Water-oxidizing or water-splitting photosynthesis was invented by cyanobacteria approximately 2.4 billion years ago and then borrowed by other groups of organisms thereafter,” explains Woodward Fischer, assistant professor of geobiology at Caltech and a coauthor of the study. “Algae borrowed this photosynthetic system from cyanobacteria, and plants are just a group of algae that took photosynthesis on land, so we think with this finding we’re looking at the inception of the molecular machinery that would give rise to oxygen.”

Read more at: Phys.org

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