Life Before Oxygen


One of the well known facts is that oxygen is one of the most essential requirements of life; without it, organisms on Earth would not survive. However, what if I tell you that researchers have recently discovered bacteria fossils that lived without oxygen; they were found in a rock formation in South Africa, dating back to almost 2.5 billion years.

Those ancient life forms were found in two separate locations in South Africa, where they lived in a very dark deep water environment, with an atmosphere of much less than one percent oxygen. Scientists have presumed that there were organisms living in deep water and in the mud that did not need sunlight nor oxygen, but they did not have any direct evidence for them until now.

This kind of bacteria existed two billion years before plants and trees, which evolved about 450 million years ago, and had to adapt the changes in atmospheric concentrations of carbon dioxide, nitrogen, and oxygen. It consumed the molecules dissolved from sulfur-rich minerals, which were from land rocks that had eroded and washed out to sea, or from the volcanic remains on the ocean’s floor.

The sulfur-oxidizing bacteria are described by scientists as exceptionally large, spherical-shaped, smooth-walled microscopic structures much larger than most modern bacteria. They are similar to some modern single-celled organisms that live in deep water, sulfur-rich ocean settings today, where even there are almost no traces of oxygen now.

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Scientists are excited by this discovery, as it is not like many of the bacteria and microorganisms found on Earth, which thrive on the presence of oxygen; a proof that it is a microorganism that existed prior the “Great Oxidation Event”, in which massive amounts of oxygen dissolved into the atmosphere.



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SCIplanet is a bilingual edutainment science magazine published by the Bibliotheca Alexandrina Planetarium Science Center and developed by the Cultural Outreach Publications Unit ...
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