JUL 19, 2019 6:32 AM PDT

Competition of Different Photosynthesis Mechanisms might Have Slowed Down Oxygenation of the Prehistoric Earth

WRITTEN BY: Daniel Duan

(Pixabay)

Long before Earth became a hotbed for a diversity of life forms, its atmosphere had almost no oxygen. Thanks to the emergence of photosynthesis inside primordial microbes, our planet gradually switched to an oxygen-rich atmosphere.

In a recent publication, a group of U.S. and Canadian microbiologists reported that if it is not for anoxygenic photosynthesis, an older form of photosynthesis, our planet could have gotten its oxygen almost one billion years earlier.

At the very beginning of Earth's existence, its atmosphere was primarily hydrogen, the left-over of the making of a star—our sun, with a small amount of water vapor, methane, and ammonia. Then came the volcanic activity and bombardment of asteroids, adding nitrogen, carbon dioxide, and noble gases to the atmosphere.

About 3 billion years ago, the bio-transformation of our planet finally occurred with the emergence of oxygenic photosynthesis, a process that converts electromagnetic energy (light) into chemical fuel (sugars) with oxygen released as a byproduct. These days, most plants, algae, and cyanobacteria perform this type of photosynthesis. But the math does not add up as scientists looked closer into the time it took for oxygen gas to rise up our atmosphere—it was way too long.

So what slowed down the oxygenation of Earth?

Using a multi-disciplinary approach that combines experimental microbiology, genomic analyses, and Earth system modeling, researchers at the University of British Columbia in Vancouver, BC and NASA's Astrobiology Institute took a deep dive into the prehistoric biosphere, and traced the cause to an unusual suspect—the iron(Fe)-oxidizing microbes.

Around 2.5 billion years ago, with almost no oxygen in the atmosphere, Earth's early oceans were rich in ferrous (Fe(II)). With easy access to Fe(II) and carbon dioxide in the air, the ancient anoxygenic photosynthesizers can generate their fuel. The process generates Fe(III) oxide, basically rust, as the by-product instead of oxygen gas.

Multiple lines of evidence in the joint research showed that the iron-oxidizing, photosynthesizing microbes are “fierce competitors for light and nutrients,” which led to a slow global oxygen release.

Commenting on their work, Kazumi Ozaki, the first author and a newly appointed assistant professor at Japan's Toho University said: “We propose that their ability to outcompete oxygen-producing photosynthesizers is an important component of Earth’s global oxygen cycle.”

What's more intriguing, the team of microbiologists also believed that they found a potential feedback loop within the coupled nutrient cycle (including essential elements such as carbon, phosphate, oxygen, and iron) among all creatures at the time, which might have tipped the balance in the favor of oxygenic photosynthesis.

That Time Oxygen Almost Killed Everything (PBS Eons)

This feedback mechanism could have caused the "runaway planetary oxygenation", during which the amount of atmospheric O2 rose quickly and substantially. The altered atmospheric pressure increased oxygen concentration in the seawater and subsequently had most Fe(II) oxidized into rust, eliminating the sole life-dependent substrate for all iron-oxidizing microbes.

Their results not only led to a deeper understanding of intertwining relationship between the evolution of early life forms and the transformation of Earth’s atmosphere, but also provided astrobiologists a sneak peek into how oxygenation could happen on exoplanets.

This latest research was published in the journal Nature.

Source: ZME Science

About the Author
  • Graduated with a bachelor degree in Pharmaceutical Science and a master degree in neuropharmacology, Daniel is a radiopharmaceutical and radiobiology expert based in Ottawa, Canada. With years of experience in biomedical R&D, Daniel is very into writing. He is constantly fascinated by what's happening in the world of science. He hopes to capture the public's interest and promote scientific literacy with his trending news articles. The recurring topics in his Chemistry & Physics trending news section include alternative energy, material science, theoretical physics, medical imaging, and green chemistry.
You May Also Like
SEP 10, 2020
Chemistry & Physics
Reprogramming Virus to Build Better Li-ion Batteries
SEP 10, 2020
Reprogramming Virus to Build Better Li-ion Batteries
There's no doubt that the word "virus" is currently on everyone's mind. However, there's a lot mor ...
OCT 05, 2020
Chemistry & Physics
Improving microbial elecrosynthesis
OCT 05, 2020
Improving microbial elecrosynthesis
New research from a KAUST team highlights the development of a semiconductive photocatalyst that recycles CO2 and c ...
OCT 26, 2020
Chemistry & Physics
Fighting mesothelioma with gold nanotubes
OCT 26, 2020
Fighting mesothelioma with gold nanotubes
New research published in the journal Small details how gold nanotubes could be used to treat mesothelioma cancer. ...
OCT 28, 2020
Chemistry & Physics
Paleontologists use scanning electron microscopy to analyze dinosaur egg fossils
OCT 28, 2020
Paleontologists use scanning electron microscopy to analyze dinosaur egg fossils
Scientists report using scanning electron microscopy to examine the surfaces of dinosaur egg fossils in order to determi ...
NOV 13, 2020
Chemistry & Physics
Mid-IR Spectroscopy a Convenient, Accurate Means of Cancer Diagnosis
NOV 13, 2020
Mid-IR Spectroscopy a Convenient, Accurate Means of Cancer Diagnosis
Last Sunday, November 8, was the International Day of Radiology (IDoR 2020), an event celebrated by radiologists, techno ...
NOV 22, 2020
Chemistry & Physics
New material removes copper ions from wastewater
NOV 22, 2020
New material removes copper ions from wastewater
A promising solution relies on materials that capture heavy metal atoms, such as copper ions, from wastewater through a ...
Loading Comments...