Earth's biggest murder mystery: Methane-spewing microbe named prime suspect

An increase in the concentration of nickel near the end of the Permian period enabled microorganisms to increase methane production, causing an extinction event known as the Great Dying, say scientists.

Suzhong Shen
This illustrates the section of sedimentary rock that spans the Permian-Triassic transition. Samples from these sections were used to measure the amount of carbon and nickel released at this time.

Scientists might have just solved one of the world's oldest murder mysteries, an "ancient whodunit" perpetrated some 250 million years ago.

By examining evidence collected from the crime scene – basically the entire planet – scientists concluded that the mass extinction that occurred toward the end of the Permian period, in which more than 90 percent of all species were wiped out, was caused by methane-belching microbes.

Many researchers had earlier suggested that volcanic eruptions in Siberia had released large amounts of carbon dioxide and other gases in the Earth's atmosphere. An increase in the carbon dioxide levels, they hypothesized, disrupted the atmospheric carbon cycle and caused the mass extinction.

But that hypothesis didn't add up. “A rapid initial injection of carbon dioxide from a volcano would be followed by a gradual decrease,” Gregory Fournier of Massachusetts Institute of Technology and second author of the paper said in a press release. “Instead, we see the opposite: a rapid, continuing increase.”

Then what caused "the Great Dying," as the Permian-Triassic extinction event is known?

To find the culprit, researchers began by looking at geochemical evidence and examining carbon isotopes that suggested an increase in organic carbon concentrations within the oceans.

Anoxic conditions in the sea at that time caused an increase in organic matter. But researchers say they do not know how those anoxic conditions came about. Hence, over a period of time a lot of organic carbon was being deposited into the oceans.

And it was during this period that Methanosarcina – a genus of microorganisms that produce methane – suddenly bloomed within the oceans in large numbers, radically altering the climate and the ocean cycles.

After analyzing genomes of "descendants and ancestors of Methanosarcina" MIT geophysics professor Daniel Rothman and his team noted that it was during the mass extinction that these microbes acquired "new microbial metabolic pathway."

Dr. Rothman's team proposes that this pathway resulted in runaway methane production, which might have caused the extinction, according to the findings of the paper titled "Methanogenic burst in the end-Permian carbon cycle" published in the Proceedings of the National Academy of Science. 

Moreover, volcanic eruptions that spewed large amounts of nickel helped these microbes to release methane at a faster rate, says Dr. Fournier.

For Methanosarcina, nickel is the "limiting nutrient," says Dr. Rothman. More nickel means more activity for the microbes. Sediment deposits suggest that concentration of nickel did increase during that time when mass extinction occurred.

"Finally, we show that nickel concentrations in South China sediments increased sharply at the extinction, probably as a consequence of massive Siberian volcanism, enabling a methanogenic expansion by removal of nickel limitation. Collectively, these results are consistent with the instigation of Earth’s greatest mass extinction by a specific microbial innovation," researchers note in their paper.

 “The cumulative impact of all these things is much more powerful than any one individually," Rothman says. The volcanic eruptions acted more as catalyst for the process than singlehandedly causing the extinction, he says.

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.