Tag Archives: Great Oxygenation Event

Medical Microfiction: Stromatolites

The architects that built the world are long gone. Many aeons ago, they lived, labored, and died in mats in the shallows. Their offspring, architects also, plied the family trade atop the graves of their forebears, until they too passed. And so one biofilm atop the next, strange, striped stones emerged.

We remember them for the rocks, but the architects left something greater still. Together those venerable microbes spun sunlight into atmosphere, shaping the very air into the element which gives voice to speech and song.

We stand not on the backs of giants, but on the bones of bacteria.


English: Stromatolites growing in Hamelin Pool...
Stromatolites: they’re rocks, but they deserve a little respect. They oxygenated the atmosphere! (Photo credit: Wikipedia)

Stromatolites are not technically “medical”, but they’re certainly a nifty piece of science, and one I was dying to share with you! First, let’s dissect the word. “Stroma” comes from a Greek word meaning mattress  or bed. “Lite” comes from the Greek for stone. As the story describes, stromatolites are fossilized stones that were formed by thin layers of bacteria dying off atop one another over a huge period of time. Think of them as something like coral reefs, but far older.

One of the most important ancient sources of stromatolites were the cyanobacteria responsible for transforming much of the methane in Earth’s atmosphere into oxygen, thus allowing creatures like ourselves to live, love, and breathe. We owe a lot to these little guys, and I wanted to take a moment to remember their inestimable contribution to our lush, green Earth. Those of you who have been reading my blog from the very beginning may recall that I’ve mentioned the Great Oxygenation Event once before, but I thought they were interesting enough to bring up again. I think it’s important to remember that while human beings dominate the planet now, all our accomplishments rest on the shoulders of those that did the work before us. Even the air we breathe is something to be grateful for; it came from somewhere.

What other parts of the natural world deserve our gratitude? What tends to get overlooked in our day-to-day shuffle?

Medical Microfiction: Anoxia

“Name That Extinction Event”

The researcher marveled at her discovery. It was all so elegant. The equation made perfect sense. Water plus carbon dioxide–in conjunction with sunlight–would yield all the food they needed. World hunger would end overnight. One simple gene splice and everyone could make their own food on demand.

Her colleague tapped the end of the equation. “There’s a problem. The food will be infinite, yes, and practically free. But what about this byproduct? Technically it’s poisonous, and it could lead to global cooling.”

The researcher waved him off. “Oh, I’m sure a little extra oxygen in the atmosphere won’t hurt anyone.”


Cyanobacteria (Photo credit: Argonne National Laboratory)

Did you guess The Great Oxygenation Event? If so, you’re right!

“Anoxia” means a lack of oxygen. Medically, this could mean a lack of oxygen in the blood, brain, or in the muscles. If you rely on aerobic respiration (which, if you’re human, you do), then anoxia is a Very Bad Thing. But lots of creatures out there feel the same way about oxygen as we do about carbon dioxide or methane. Hidden away in the most extreme environments on Earth, we find these extremophiles, creatures that thrive under conditions that seem hostile to life. For example,  anaerobic bacteria that live in our bowels are responsible for the, ahem, methane we expel.

These anaerobes used to rule the world. Back in the day, the Earth’s atmosphere contained practically no oxygen and tons of methane. Like carbon dioxide, methane’s a greenhouse gas, but it retains even more heat than carbon dioxide. If carbon dioxide’s a light jacket, then methane’s a parka. This really wasn’t a problem for the extremophiles since they thrived in these conditions.

AIRS maps the distribution of carbon dioxide i...
AIRS maps the distribution of carbon dioxide in the atmosphere. (Photo credit: Wikipedia)

Enter some enterprising cyanobacteria. These little guys pioneered the art of photosynthesis, harvesting the power of the sun to make food. As the cyanobacteria pumped out oxygen like a boss, the methane in the atmosphere converted to carbon dioxide, and gradually the oxygen levels rose as well, causing a drop in global temperatures. These conditions led to global freezing and mass extinction of many forms of anaerobic life.

If cyanobacteria were sentient, you have to wonder if they’d think about the ramifications of inventing photosynthesis. Would they believe their small actions could have such a big impact on the world? Would they hold debates on climate change and weigh the benefits against the costs? Would they have any pity or regret for driving the anaerobes to such hard times, in some cases literally living in crap for survival?

But I’m sure a little extra oxygen in the atmosphere isn’t going to hurt anyone.

In the wake of last week’s historic high benchmark of carbon dioxide in the atmosphere, this is worth thinking about. What questions should shape our ethic for how we treat our environment?