Great Oxygenation Event: MIT Scientists’ New Hypothesis for One of the Grand Mysteries of Science

Around 2.3 billion years ago, oxygen began building up in the atmosphere, eventually reaching the life-sustaining levels we breathe today. A new hypothesis proposed by MIT scientists suggests a mechanism for how this may have happened. Pictured are examples of Paleoproterozoic organisms. Credit: MIT News

Microbes and Minerals May Have Set Off Earth’s Oxygenation

Scientists propose a new mechanism by which oxygen may have first built up in the atmosphere.

For the first 2 billion years of Earth’s history, there was barely any oxygen in the air. While some microbes were photosynthesizing by the latter part of this period, oxygen had not yet accumulated at levels that would impact the global biosphere.

But somewhere around 2.3 billion years ago, this stable, low-oxygen equilibrium shifted, and oxygen began building up in the atmosphere, eventually reaching the life-sustaining levels we breathe today. This rapid infusion is known as the Great Oxygenation Event, or GOE. What triggered the event and pulled the planet out of its low-oxygen funk is one of the great mysteries of science.

A new hypothesis, proposed by MIT scientists, suggests that oxygen finally started accumulating in the atmosphere thanks to interactions between certain marine microbes and minerals in ocean sediments. These interactions helped prevent oxygen from being consumed, setting off a self-amplifying process where more and more oxygen was made available to accumulate in the atmosphere.

The scientists have laid out their hypothesis using mathematical and evolutionary analyses, showing that there were indeed microbes that existed before the GOE and evolved the ability to interact with sediment in the way that the researchers have proposed.

Their study, appearing today in Nature Communications, is the first to connect the co-evolution of microbes and minerals to Earth’s oxygenation.

“Probably the most important biogeochemical change in the history of the planet was oxygenation of the atmosphere,” says study author Daniel Rothman, professor of geophysics in MIT’s Department of Earth, Atmospheric, and Planetary Sciences (EAPS). “We show how the interactions of microbes, minerals, and the geochemical environment acted in concert to increase oxygen in the atmosphere.”

The study’s co-authors include lead author Haitao Shang, a former MIT graduate student, and Gregory Fournier, associate professor of geobiology in EAPS.

A step up

Today’s oxygen levels in the atmosphere are a stable balance between processes that produce oxygen and those that consume it. Prior to the GOE, the atmosphere maintained a different kind of equilibrium, with producers and consumers of oxygen in balance, but in a way that didn’t leave much extra oxygen for the atmosphere.

What could have pushed the planet out of one stable, oxygen-deficient state to another stable, oxygen-rich state?

“If you look at Earth’s history, it appears there were two jumps, where you went from a steady state of low oxygen to a steady state of much higher oxygen, once in the Paleoproterozoic, once in the Neoproterozoic,” Fournier notes. “These jumps couldn’t have been because of a gradual increase in excess oxygen. There had to have been some feedback loop that caused this step-change in stability.”

He and his colleagues wondered whether such a positive feedback loop could have come from a process in the ocean that made some organic carbon unavailable to its consumers. Organic carbon is mainly consumed through oxidation, usually accompanied by the consumption of oxygen — a process by which microbes in the ocean use oxygen to break down organic matter, such as detritus that has settled in sediment. The team wondered: Could there have been some process by which the presence of oxygen stimulated its further accumulation?

Shang and Rothman worked out a mathematical model that made the following prediction: If microbes possessed the ability to only partially oxidize organic matter, the partially-oxidized matter, or “POOM,” would effectively become “sticky,” and chemically bind to minerals in sediment in a way that would protect the material from further oxidation. The oxygen that would otherwise have been consumed to fully degrade the material would instead be free to build up in the atmosphere. This process, they found, could serve as a positive feedback, providing a natural pump to push the atmosphere into a new, high-oxygen equilibrium.

“That led us to ask, is there a microbial metabolism out there that produced POOM?” Fourier says.

In the genes

To answer this, the team searched through the scientific literature and identified a group of microbes that partially oxidizes organic matter in the deep ocean today. These microbes belong to the bacterial group SAR202, and their partial oxidation is carried out through an enzyme, Baeyer-Villiger monooxygenase, or BVMO.

The team carried out a phylogenetic analysis to see how far back the microbe, and the gene for the enzyme, could be traced. They found that the bacteria did indeed have ancestors dating back before the GOE, and that the gene for the enzyme could be traced across various microbial species, as far back as pre-GOE times.

What’s more, they found that the gene’s diversification, or the number of species that acquired the gene, increased significantly during times when the atmosphere experienced spikes in oxygenation, including once during the GOE’s Paleoproterozoic, and again in the Neoproterozoic.

“We found some temporal correlations between diversification of POOM-producing genes, and the oxygen levels in the atmosphere,” Shang says. “That supports our overall theory.”

To confirm this hypothesis will require far more follow-up, from experiments in the lab to surveys in the field, and everything in between. With their new study, the team has introduced a new suspect in the age-old case of what oxygenated Earth’s atmosphere.

“Proposing a novel method, and showing evidence for its plausibility, is the first but important step,” Fournier says. “We’ve identified this as a theory worthy of study.”

Reference: “Oxidative metabolisms catalyzed Earth’s oxygenation” by Haitao Shang, Daniel H. Rothman and Gregory P. Fournier, 14 March 2022, Nature Communications.
DOI: 10.1038/s41467-022-28996-0

This work was supported in part by the mTerra Catalyst Fund and the National Science Foundation.

Atmospheric ScienceBiochemistryEvolutionGeologyMicroorganismsMITPopular
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  • Clyde Spencer

    “These jumps couldn’t have been because of a gradual increase in excess oxygen. There had to have been some feedback loop that caused this step-change in stability.”

    An obvious “feedback loop” for which there is abundant evidence in the form of ‘banded iron formations,’ is that once a 2 billion year accumulation of iron ions was oxidized and precipitated out as chemical sediments, there was little to restrain newly formed oxygen from outgassing from the oceans and accumulating in the atmosphere.

  • John Bayer

    IIRC peak oxygen levels are dated to the Mesozoic.

    • Clyde Spencer

      Because by then there weren’t just organisms in the ocean, but the land was covered by plants which also contributed oxygen.

  • mullach abu

    its the iron magnesium core that causes mark i
    Paleoproterozoic steady state of low oxygen to a steady state of much higher oxygen
    Spike in oxygen i the number of species that acquire the gene increased significantly
    Bacterial group sar 202 partial oxidation through enzyme Baeyer villiger monooxygenase or bvmo ancestor in pre goe times
    Its the microbes and bacterium age mark i the age of slime and mould
    2,400,000,000 its the iron magnesium core that causes mark ii
    Neoproterozoic steady state of much higher oxygen to a much higher state of higher oxygen levels
    Spike in oxygen ii the number of species that acquire the gene increased significantly
    Bacterial group sar 202 partial oxidation through enzyme Baeyer villiger monooxygenase or bvmo ancestor in pre goe times
    There has to be some feed back loop that caused this step change in stability
    Its the microbes and bacterium age mark ii the age of slime and mould of fungi mosses ferns
    THE EVENT OF THE !4TH BILLENIUM
    560,000,000 its the iron nickel core that cuases mark iii its the age of plants
    500,000,000 its the iron and nickel core that causes mark iv the age of trees
    400,000,000 its the iron and nickel core that causes mark v the age of giant beasts
    64,000,000 its the iron and nickel core that causes mark vi the age of mammals
    6,000,000 its the iron and nickel core that causes mark vii the age of homo noble
    2022 its the iron and nickel core that causes mark viii modern noble homo to reckon the space time continuum like reading the pages of a book read the signs of the times read the bed of rocks
    Which brings me to my question
    What ocean rock layers are you analysing 2,400,000,000 years ago where are they located and what minerals are on them as ocean sediment

  • Babu G. Ranganathan

    Babu G. Ranganathan*
    (B.A. Bible/Biology)

    THE CELL could not have evolved. A partially evolved cell would quickly disintegrate under the effects of random forces of the environment, especially without the protection of a complete and fully functioning cell membrane. A partially evolved cell cannot wait millions of years for chance to make it complete and living! In fact, it couldn’t have even reached the partially evolved state.

    CATCH-22 FOR EVOLUTIONARY ORIGIN OF LIFE

    Just having the right materials, elements, and conditions do not mean that life can arise by chance.

    Miller, in his famous experiment in 1953 showed that individual amino acids (the building blocks of life) could come into existence by chance. But, it’s not enough just to have amino acids. The various amino acids that make-up life must link together in a precise sequence, just like the letters in a sentence, to form functioning protein molecules. If they’re not in the right sequence the protein molecules won’t work. It has never been shown that various amino acids can bind together into a sequence by chance to form protein molecules. Even the simplest cell is made up of many millions of various protein molecules.

    What many don’t realize is that although oxygen is necessary for life’s processes, the presence of oxygen would prevent life from coming into being. This is because oxygen is destructive unless there are mechanisms already in place to control, direct, and regulate it, such as what we find in already existing forms of life.

    RNA and DNA are made up of molecules (nucleic acids) that must also exist in the right sequence. Furthermore, none of these sequential molecules, proteins, DNA, RNA, can function outside of a complete and living cell and all are mutually dependent on one another. One cannot come into existence without the other.

    Mathematicians have said any event in the universe with odds of 10 to 50th power or greater is impossible! The probability of just a single average size protein molecule arising by chance is 10 to the 65th power. The late great British scientist Sir Frederick Hoyle calculated that the odds of even the simplest cell coming into existence by chance is 10 to the 40,000th power! How large is this? Consider that the total number of atoms in our universe is 10 to the 82nd power.

    The cell could not have evolved. A partially evolved cell would quickly disintegrate under the effects of random forces of the environment, especially without the protection of a complete and fully functioning cell membrane. A partially evolved cell cannot wait millions of years for chance to make it complete and living! In fact, it couldn’t have even reached the partially evolved state.

    Alien beings, even if they do exist, could not have evolved. How could they have survived millions of years while the very biological structures, organs, and systems necessary for their survival were supposedly still evolving? Life, in any form (even a single-celled organism), must be complete, fully integrated, and fully-functioning from the very start to be fit for survival.

    Of course, once there is a complete and living cell then the code and mechanisms exist to direct the formation of more cells. The problem for evolutionists is how did the cell originate when there were no directing code and mechanisms in nature. Natural laws may explain how a cell or airplane works but mere undirected natural laws could not have brought about the existence of either.

    What about synthetic life? Scientists didn’t create life itself. What they’ve done is, by using intelligent design and sophisticated technology, scientists built DNA code from scratch and then they implanted that man-made DNA into an already existing living cell and alter that cell. That’s what synthetic life is.

    Through genetic engineering scientists have been able to produce new forms of life by altering already existing forms of life, but they have never created life from non-living matter. Even if they do, it won’t be by chance but by intelligent design. That doesn’t help the theory of evolution.

    What about natural selection? Natural selection doesn’t create or produce anything. It can only “select” from biological variations that are possible and which have survival value. If a variation occurs that helps a species survive, that survival is called ” natural selection.” It’s a passive process. There’s no conscious selection by nature, and natural selection only operates in nature once there is life and reproduction and not before, so it would not be of assistance to the origin of life.

    Science can’t prove we’re here by chance or design. Neither was observed. Both are positions of faith. The issue is which faith is best supported by science. Let the scientific arguments of both sides be presented.

    Read my popular Internet articles:

    THE NATURAL LIMITS TO EVOLUTION
    ANY LIFE ON MARS CAME FROM EARTH

    Visit my Internet site: THE SCIENCE SUPPORTING CREATION

    Author of the popular Internet article, TRADITIONAL DOCTRINE OF HELL EVOLVED FROM GREEK ROOTS

    *I have given successful lectures (with question and answer period afterwards) defending creation before evolutionist science faculty and students at various colleges and universities. I’ve been privileged to be recognized in the 24th edition of Marquis “Who’s Who in The East” for my writings on religion and science.

  • Bill Thiel

    I always figured the oxygen being created, early on, was consumed by oxygenating minerals which is why we have such Red Rock accumulations throughout the world. After such time there was not as much “dirt” to “rust”, the oxygen then began to accumulate in the atmosphere. Seems pretty simple and logical.

  • rob

    The American geologist, Preston Cloud, said it first, back in the late-1960s early-1970s.Whilst the finer details of genetics, cell metabolism and feedback loops are now being investigated, the all-important concept linking the development of the eukaryotic cell, photosynthesis and the GOE is now around half a century old. Fascinating stuff.

  • Sekar

    Very Interesting.

    1. Are Planets and the Moons “”Chips of the Old Block our Sun in the Sky or were they formed independently from the gases floting around and turning into Liquids and Solids, around which Star Duust from the rest of the Universe accreted?

    2. There are 118 elemnts in the periodic table. Animate Life bearing beings appear to be Carbon, Oxygen , Nitrogen, , and a few trace elements of other elements from the 118.

    3. Looking at Earth as the baseline, we have seen the evolution of two broad species of beings. One breathes carbon-di-oxide and and releases oxygen (Trees) and the other breathes oxygen and releases carbon di oxide (Non-Trees). My good frend Dwight Lauer in the school of Forrestry at UGA and my appartmate ,used to crack this Forrestor Joke when he wanted me to make myself scarce. ” Make like a Tree and Leave!!”

    4, The Atmospheric Balance between Nitrogen (dominant ~ 78 % ), Oxygen (~20,88 %) and traces of Carbon-Di-Oxde and Water Vapour and rare gases on the Planet Earth has been able to sustain life. The question we need to ask is did the atmosphere create conditions for life to emerge or did life create the atmospheric conditions necessary to help Life Thrve. It is the same Chicjen or Egg connundrum. Which came first?

    5. If in the first two billion years there was barely any oxygen in the air, what exactly did the air consist of? Composition of air and its constituent gases would be interesting to know, before the Oxidative “Oxygen ” with atomc number 8 intruded.

    6. The mechanism to explain the increasing concentration of Oxygen in the atmosphere seems a plausible explanation.

    7. The reason is that ancient Vedic Science teaches us that:
    Life existed first,
    then we got consciousness,
    followed by ability to breathe,
    then life developed a circulatory system,
    then excetory system,
    and then a creative -intuitive faculty / capability

    and learnt to reproduce copies of itself along the way to create complex life in all its
    varied diversity that we see around us.

    Developing a holistic and comprehensive theory of evolution and extinction of species may be a good idea. At least we will have a better understanding of the Physcal Body of various species.

    Views expressed are ppersonal and not binding on anyone.