Oxygen consumers and oxygen producers make up most of the life on Earth.
The concentration of oxygen in the atmosphere is 21 percent. That was not always the case.
Oxygen was not plentiful in the first billion years of Earth&s existence. The diatomic gas suddenly increased.
How did more oxygen being given than taken happen?
Researchers at the Massachusetts Institute of Technology have a new hypothesis for the mysteries that have been pondered for years. The line between oxygen producers and consumers may be being crossed by some microbes.
Oxygen is used by Microbes in the deep ocean to break down organic matter. If another microbe was taking a bite out of the ocean&s oxygen before other consumers could get to it, what would happen?
If a microbe only partially oxidizes organic matter, there is a good chance the leftovers will bind to minerals in the ocean.
The oxygen burial would keep the organic material from being fully oxidation. Oxygen could build up in the water before it trickles out into the atmosphere. The ocean can absorb it again, creating a positive feedback loop.
"That led us to ask, is there a microbial metabolism out there that produced POOM?" recalls Gregory Fourier.
It turns out there was. Fourier and his colleagues landed on a group ofbacteria known as SAR 202.
The modern group ofbacteria can oxidize organic matter in the deep oceans. It can do this by using the Baeyer-villiger monooxygenase.
The authors found that the genes for this enzyme were found among microbes that had evolved before the oxidation event.
The spike in early Earth oxygen appears to coincide with the expansion of this gene. As the ability to partially oxidize organic material spread among microbes, there was also an increase in atmospheric oxygen levels.
The timing could be a coincidence or it could be that the genes helped kick off the oxidation event.
Oxygen availability in the environment probably supported the spread of similar oxidations in other microbes.
The authors write that it may appear counter-intuitive to consume O2 after all.
There is a potentially important positive feedback in the interaction of oxidation products with minerals.
Mineral surfaces in the ocean are more tightly bound to partially oxidized organic matter. This means that the microbes cannot get to it easily.
Oxygen can accumulate in Earth's oceans and atmosphere because of the buried oxygen.
At some point, the positive feedback loop would have balanced out the oxygen in the atmosphere and life forms would have started consuming it.
Oxygen consumers and producers have a scale.
A recent study supports the idea that the burial of organic matter in a low oxygen environment played a bigger role in Earth's great oxygenation event than we thought.
Instead of photosynthesizingbacteriaoxygenating the atmosphere and then the ocean, what if minerals in the oceanoxygenated the atmosphere?
These ideas seem like possible explanations so far, but more research is needed.
The first step is to show evidence for a novel method.
Nature Communications published the study.
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