Cylindrospermum - Blue Green Algae, microscope photograph

Modern microbes provide window into ancient ocean


Research News

Step into your new, microscopic time machine. Scientists at the University of Colorado Boulder have discovered that a type of single-celled organism living in modern-day oceans may have a lot in common with life forms that existed billions of years ago–and that fundamentally transformed the planet.

The new research, which will appear Jan. 6 in the journal Science Advances, is the latest to probe the lives of what may be nature’s hardest working microbes: cyanobacteria.

These single-celled, photosynthetic organisms, also known as “blue-green algae,” can be found in almost any large body of water today. But more than 2 billion years ago, they took on an extra important role in the history of life on Earth: During a period known as the “Great Oxygenation Event,” ancient cyanobacteria produced a sudden, and dramatic, surge in oxygen gas.

“We see this total shift in the chemistry of the oceans and the atmosphere, which changed the evolution of life, as well,” said study lead author Sarah Hurley, a postdoctoral research associate in the departments of Geological Sciences and Biochemistry. “Today, all higher animals need oxygen to survive.”

To date, scientists still don’t know what these foundational microbes might have looked like, where they lived or what triggered their transformation of the globe.

But Hurley and her colleagues think they might have gotten closer to an answer by drawing on studies of naturally-occurring and genetically-engineered cyanobacteria. The team reports that these ancient microbes may have floated freely in an open ocean and resembled a modern form of life called beta-cyanobacteria.

Studying them, the researchers said, offers a window into a time when single-celled organisms ruled the Earth.

“This research gave us the unique opportunity to form and test hypotheses of what the ancient Earth might have looked like, and what these ancient organisms could have been,” said co-author Jeffrey Cameron, an assistant professor of biochemistry.

Take a breath

You can still make the case that cyanobacteria rule the planet. Hurley noted that these organisms currently produce about a quarter of the oxygen that comes from the world’s oceans.

One secret to their success may lie in carboxysomes–or tiny, protein-lined compartments that float inside all living cyanobacteria. These pockets are critical to the lives of these organisms, allowing them to concentrate molecules of carbon dioxide within their cells.

“Being able to concentrate carbon allows cyanobacteria to live at what are, in the context of Earth’s history, really low carbon dioxide concentrations,” Hurley said.

Before the Great Oxidation Event, it was a different story. Carbon dioxide levels in the atmosphere may have been as much as 100 times what they are today, and oxygen was almost nonexistent. For that reason, many scientists long assumed that ancient microorganisms didn’t need carboxysomes for concentrating carbon dioxide.

“Cyanobacteria have persisted in some form over two billion years of Earth’s history,” she said. “They could have been really different than today’s cyanobacteria.”

To find out how similar they were, the researchers cultured jars filled with bright-green cyanobacteria under conditions resembling those on Earth 2 billion years ago.

Hurley explained that different types of cyanobacteria prefer to digest different forms, or “isotopes,” of carbon atoms. As a result, when they grow, die and decompose, the organisms leave behind varying chemical signatures in ancient sedimentary rocks.

“We think that cyanobacteria were around billions of years ago,” she said. “Now, we can get at what they were doing and where they were living at that time because we have a record of their metabolism.”

Resurrecting zombie microbes

In particular, the team studied two different types of cyanobacteria. They included beta-cyanobacteria, which are common in the oceans today. But the researchers also added a new twist to the study. They attempted to bring an ancient cyanobacterium back from the dead. Hurley and her colleagues used genetic engineering to design a special type of microorganism that didn’t have any carboxysomes. Think of it like a zombie cyanobacterium.

“We had the ability to do what was essentially a physiological resurrection in the lab,” said Boswell Wing, a study coauthor and associate professor of geological sciences.

But when the researchers studied the metabolism of their cultures, they found something surprising: Their zombie cyanobacterium didn’t seem to produce a chemical signature that aligned with the carbon isotope signatures that scientists had previously seen in the rock record. In fact, the best fit for those ancient signals were likely beta-cyanobacteria–still very much alive today.

The team, in other words, appears to have stumbled on a living fossil that was hiding in plain sight. And, they said, it’s clear that cyanobacteria living around the time of the Great Oxygenation Event did have a structure akin to a carboxysome. This structure may have helped cells to protect themselves from growing concentrations of oxygen in the air.

“That modern organisms could resemble these ancient cyanobacteria–that was really counterintuitive,” Wing said.

Scientists, they note, now have a much better idea of what ancient cyanobacteria looked like and where they lived. And that means that they can begin running experiments to dig deeper into what life was like in the 2 billion-year-old ocean.

“Here is hard evidence from the geological record and a model organism that can shed new light on life on ancient Earth,” Cameron said.


Other coauthors on the new paper included CU Boulder undergraduate student Claire Jasper and graduate student Nicholas Hill.

From EurekAlert!

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January 8, 2021 3:06 am

This study is a start on the path to removing the idea that CO2 is a pollutant. The more these young scientist discover CO2 as a function of “life”, perhaps the sooner we will end the reign of CO2 driven climate doom hysteria.

January 8, 2021 3:49 am

Science as per Richard Feynman’s instructions:

  1. Make a guess.
  2. Design an experiment to test your guess.
  3. If the results of the experiment disagree with data then your guess is wrong.

Real scientists at work.

Frank from NoVA
January 8, 2021 4:43 am

“Before the Great Oxidation Event, it was a different story. Carbon dioxide levels in the atmosphere may have been as much as 100 times what they are today, and oxygen was almost nonexistent.”

I’m having problems with the O2 stoichiometry: 100 times (roughly) 400 ppm is, what, 4% then versus 21% today?

John Tillman
Reply to  Frank from NoVA
January 8, 2021 5:11 am

Their estimate of Paleoproterozoic atmospheric CO2 concentration is up to 4%, and for O2, close to zero. Now it’s ~400ppm for CO2 and 21% for O2.

Frank from NoVA
Reply to  John Tillman
January 8, 2021 5:55 am

That’s my question – it doesn’t foot – where did the incremental 17% of O2 come from?

John Tillman
Reply to  Frank from NoVA
January 8, 2021 6:42 am

The O2 came from CO2, which was higher then, but lower now.

No one really knows how high CO2 was in the Archean Eon and Paleoproterozoic Era of the Proterozoic Eon. When you consider all the carbonate rock and life on Earth now, there had to have been a lot. Perhaps Venusian levels.

Oxygen has accumulated. It didn’t all come from Paleoproterozoic CO2. Oxygen was still low in the Neoproterozoic Era, last of the Precambrian Supereon. Ediacaran fungi and animals didn’t need a lot of oxygen. Sponges still don’t.

It took off in the Paleozoic Era of our present Phanerozoic Eon, reaching 35% in the Carboniferous Period, thanks to the spread of land plants. It was lower than that in the Mesozoic Era and lower still in the current Cenozoic.

Frank from NoVA
Reply to  John Tillman
January 8, 2021 6:58 am

“No one really knows how high CO2 was in the Archean Eon and Paleoproterozoic Era of the Proterozoic Eon. When you consider all the carbonate rock and life on Earth now, there had to have been a lot. Perhaps Venusian levels.”

Thanks John – I’m ok that there is honest uncertainty of past conditions, unlike the dishonest certainty that “climatologists” have of future conditions.

John Tillman
Reply to  Frank from NoVA
January 8, 2021 7:28 am

The researchers may have selected 100 times as high enough to make their point.

Earth’s originally much higher CO2 levels would already have been drawn down during the Archean Eon by carbonate rock formation, even before oxygenic photosynthesis.

John Tillman
Reply to  John Tillman
January 8, 2021 7:01 am

I should add that there was a delay between the evolution of oxygenic photosynthesis and the buildup of O2 leading to the Catastrophe.

First, the iron abundant in Paleoproterozoic seas had to rust and precipitate out to form the Red Bands. Once this buffering ended with the iron supply, levels of O2 lethal to the mainly anaerobic microbes of that Era could accumulate.

Frank from NoVA
Reply to  John Tillman
January 8, 2021 7:35 am

Thanks again John. I’m aware of the rusting, but to be honest didn’t recollect that prior to your response. (Too early in the day). Having said that, that process, as well as others, was an O2 sink, so as you indicated in your prior response, there must have been a lot more than 4% of the miracle gas in the Paleozoic atmosphere.

John Tillman
Reply to  Frank from NoVA
January 8, 2021 9:20 am

Paleoproterozoic Era of Proterozoic Eon: 2.5 to 1.6 billion years ago. Followed by Mesoproterozoic Era.

Paleozoic Era of Phanerozoic Eon: 541 to 252 million years ago. Followed by Mesozoic Era.

John Tillman
Reply to  John Tillman
January 8, 2021 1:15 pm

comment image

O2 build-up in the Earth’s atmosphere. Red and green lines represent the range of the estimates while time is measured in billions of years ago (Ga).
Stage 1 (3.85–2.45 Ga): Practically no O2 in the atmosphere.
Stage 2 (2.45–1.85 Ga): O2 produced, but absorbed in oceans and seabed rock.
Stage 3 (1.85–0.85 Ga): O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer.
Stages 4 and 5 (0.85 Ga–present): O2 sinks filled, the gas accumulates

The oxygenation of the atmosphere and oceans

Recent dating of start of O2 buildup:,increases%20later%20in%20Earth's%20history.

Reply to  John Tillman
January 8, 2021 10:11 pm

This does not appear to address Frank’s question, which is a good one. I am now intrigued.
You say O2 was produced in Stage 2 but from what? There wouldn’t be enough dissolved O2 in the oceans to gas out in Stage 3 to make up the 21% we have now. The ozone content is trifling.
The iron rust beds would have pulled billions of tonnes of O2 out of the atmosphere.
The massive carbonate deposits would have needed more O2 to be added to the CO2 molecules to form CaCO3 so CO2 can’t be the source. of the atmosperic O2 content we now see today.
These rocks dwarf the amount of carbon in the atmosphere, oceans, and fossil fuels by several orders of magnitude.
A possible source is the Earth’s mantle where O2 may have been trapped at the time of formation.

John Tillman
Reply to  CRISP
January 9, 2021 2:46 pm

The big bump up in Stage 5 resulted from land plants’ liberating O2 from water taken in by their roots. Oxygen generated by photosynthesis come from water, not CO2.

John Tillman
Reply to  John Tillman
January 9, 2021 2:49 pm

Make that oxygen molecules.

John Tillman
Reply to  John Tillman
January 9, 2021 3:04 pm

In the light reaction, a photon splits H ions (protons) from the O atom in a water molecule. The free O atom combines with another to form an O2 molecule, which transpires out via one of the stomata which take in CO2 from the air. In the dark reactions, H ions compound with CO2 molecules to make sugar. The O atoms in CO2 stay with the C to form part of the sugar molecule (carbohydrate).

Paul of Alexandria
Reply to  Frank from NoVA
January 8, 2021 6:50 am

The initial bacteria metabolized other compounds, especially sulfur compounds.

John Tillman
Reply to  Paul of Alexandria
January 8, 2021 7:34 am

Yup. Hydrogen sulfide instead of water and sulfur as waste product rather than oxygen.

Oxygenic photosynthesis evolution:

John Tillman
Reply to  John Tillman
January 8, 2021 9:40 am

Powerpoint presentation:

Reconstructing the early evolution of photosynthesis

John Tillman
Reply to  John Tillman
January 8, 2021 9:54 am

Astrobiology of Earth: The Emergence, Evolution and Future of Life on a Planet in Turmoil

Anoxygenic photosynthesis dates back at least to 3.4 billion years ago.

Early photosynthetic systems, ie in 1) green and purple sulfur, 2) green and 3) purple nonsulfur bacteria, were most likely anoxygenic, using other molecules besides water as electron donors. 

As noted, green and purple sulfur bacteria are thought to have employed H and S as electron donors. Green nonsulfur bacteria used various amino and other organic acids as electron donors. Purple nonsulfur bacteria used a variety of nonspecific organic molecules. Reliance on these molecules squares with the geological evidence that the Archean atmosphere was still reducing.

Peta of Newark
January 8, 2021 5:32 am

“”Great Oxygenation Event””

Hey, look at meeeee. I’ve found something really great!
No no no, not him over there!!
Look at me me me!!

Were there (m)any other Oxation events

Science is great and Lowdo linked us to some epic science just yesterday, maybe day before’
In particular a little graphic which was lifted from Page 20 of this:

It says, indirectly, so I’m certain to get my head shot off that an extra 100ppm of CO2 increased the ‘Radiation Forcing’ by 2.3 watts per square metre.
Fine. Lovely. I didn’t know that but modern 5 year-olds are fully up-to-speed

Thus 100 times means that the Radiation Forcing at that time was..
Get ready

(hold onto something)
facepalm, I didn’t mean that, but IF you must



Ninety One Thousand Three Hundred and Ten Watts per square metre
or, for engineers amongst us, 91.31 kW per square metre

Gotta hand it to those bacteria – they were tough little things, to say the least

Reply to  Peta of Newark
January 9, 2021 9:57 am

The space station only receives about 1.4 kW per sq. meter.
This calculation may be flawed.

January 8, 2021 5:45 am

Does anyone else get worried when these people start genetically engineering things, especially bacteria and viruses, with the possibility of it getting loose into the environment?

Frank from NoVA
Reply to  rbabcock
January 8, 2021 5:57 am

Yes, was thinking that as well…

Reply to  rbabcock
January 8, 2021 6:26 am

that was my first thought – it’s not as though we have any immunity to these things or maybe we do, who knows?

John Tillman
Reply to  Redge
January 8, 2021 7:03 am

Cyanobacteria aren’t human pathogens, but they do produce lethal toxins.

I swim among their blooms in Oregon reservoirs anyway.

Reply to  John Tillman
January 8, 2021 7:47 am

yes, I know, John. It was more of a response to engineering of these microbes as rbabcock stated

Clyde Spencer
Reply to  rbabcock
January 8, 2021 11:23 am

“OK, that experiment didn’t work out as expected. We don’t need the bio-engineered critters anymore. Dump them down the sink.”

John Tillman
Reply to  Clyde Spencer
January 9, 2021 10:29 am

They probably wouldn’t last long in the wild.

John Tillman
Reply to  John Tillman
January 9, 2021 11:02 am

Lacking carboxysomes as they do.

Paul of Alexandria
January 8, 2021 6:53 am

For a really good overview of the “great rusting” see the “History of the Earth” channel’s video on “How Bad Was the Great Oxidation Event”.

John Tillman
January 8, 2021 6:56 am

While a worthwhile experiment, it assumes too simple a model of cyanobacterial evolution.

Different photosynthetic processes evolved a number of times in various bacterial lineages before Phylum Cyanobacteria developed it de novo or obtained it via horizontal gene transfer.

The key innovation by cyanobacteria was oxygenic photosynthesis, using water as the electron donor.

The next novelty was aerobic respiration. The so far final stage was nitrogen fixation, which not all cyanobacteria can do. Along the way, cyanobacteria were captured by eukaryotes to become chloroplasts.

So it’s not really surprising that structures to concentrate and isolate CO2 evolved fairly early. Aerobic respiration would have favored selection for this capacity.

Reply to  John Tillman
January 8, 2021 8:48 am

Just curious whether their genetic engineering is a form of horizontal gene transfer. How much is known about the vector back then – was it a virus?
Also is the capture by eukaryotes a form of gene transer or more a symbiont – parasite effect?
And what about mitochondria with their own genes?

John Tillman
Reply to  bonbon
January 8, 2021 9:31 am

Their genetic engineering involved removing a feature, not inserting a new one. It’s in effect the opposite of HGT. Cyanobacteria evolved carboxysomes on their own as a novel feature, so no vector or source required.

The capture of proteobacteria by archaea to produce eukaryotic mitchondria was endosymbiosis, not HGT. However, over time, much of the mitochondrial genome has migrated into the nucleus, the distinguishing feature of eukaryotes. Mitochondria retain some of their original genes, but might keep losing more.

I wrote a post on discovery of the probable way in which our archaean ancestor engulfed the first proto-mitochondrion, which monumental event in the history of life on Earth appears to have happened just once.

Reply to  bonbon
January 9, 2021 4:48 am

Missed that link, very interesting.
About mitochondria, often called cell power plants with ATP, did a clever archaean engulf an chemical engine and get a huge energy boost, a huge evolutionary advantage?
Did another engulf chloroplasts and harness sunlight, also a huge boost?
Which occurred first? How does such “engulfing” work?

Our economies engulf oil, uranium, and soon fusion plasma, and get a huge energy boost. It seems this process is quite natural, and very stepped, and actually directed towards higher energy flux density.

One could even say the Biosphere has engulfed this planet, changed it completely, and the atmosphere too.

Last edited 1 month ago by bonbon
John Tillman
Reply to  bonbon
January 9, 2021 10:28 am

My blog about Japanese research on archaea shows how the engulfing probably happened, essentially with tendrils.

Eukaryotes got nuclei and mitochondria before chloroplasts and other organelles. Both acquisitions were obviously huge success stories.

Reply to  John Tillman
January 15, 2021 8:20 am

I know a few well known firms where M&A (Merger and acquisition) turned sour. Maybe stakeholders got a virus 🙂

John Tillman
January 8, 2021 7:25 am

All animals (Metazoa), period, need oxygen to survive, whether higher or lower. So too do Protozoa and fungi and even plants, ie for root cells which can’t make their own oxygen, lacking sunlight.

As noted, however, the O2 needs of sponges are remarkably low. Since they often form symbiotic relationships with cyanobacteria, the combo can be a net producer of oxygen.

John Tillman
January 8, 2021 1:26 pm

In 2018, a researcher suggested that the first step in oxygenic photosynthesis predated cyanobacterial photosynthesis by about a billion years:

Early Archean origin of heterodimeric Photosystem I

Reply to  John Tillman
January 9, 2021 5:15 am

“using sequence comparisons and Bayesian relaxed molecular clocks that this gene duplication event may have occurred in the early Archean more than 3.4 billion years ago,”
That is statistical modeling.
What about actual isotope relative abundances?
He does in fact provde multiple links to isotopic data…

John Tillman
Reply to  bonbon
January 9, 2021 10:25 am

Yes, it’s a rocks and clocks, belt and braces kind of paper.

John Tillman
Reply to  John Tillman
January 9, 2021 4:59 pm

Cyanobacteria probably evolved oxygenic photosynthesis on land, not in the ocean.

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