Slow-Motion Microbes Still Living off Dino-era "Lunch Box"

Unidentified life-forms "breach the limits of life as we know it."

Dear Chris,

I do not know which species it. If I did it would with near 100% probability be one of the wrong ones because there is no overlap between described species and those that we study in the subsurface. Rikke Meyer is unfortunately in Thailand and I can not ask her.

It is accurate to caption the image as a bacterium that resembles those found in the deep sediments. You can also write that it is a bacterium that like those found in the deep sediments. Note that there are thousands of different kinds down there.

/Hans

From: Chris Combs [chcombs@ngs.org]

Sent: 16 May 2012 23:10

To: Hans Røy

Subject: Re: Science - Bacteria - National Geographic News

Hi Hans--Thank you, this is quite helpful!

Could you tell me more about which species of bacterium is depicted in Dr. Meyer's image?

Is it accurate to caption the image as a bacterium that resembles those found in the deep sediments?

Many thanks,

Chris

On Wed, May 16, 2012 at 4:35 PM, Hans Røy <hans.roy@biology.au.dk> wrote:

Dear Chris Combs,

These organisms are not very photogenic. Basically they are small round balls looking like any other common bacterium. We therefore did not go trough the significant fuzz og making good images. Not that we could have brought the equipment with us anyway.

I have attached an Atomic Force Micro-graph of a bacterium of the right morphology that you can use if you wish. It is from our press set and can be used without infringing any copyright. The picture has been taken by Dr. Rikke Meyer in our lab and any credit should be paid to her.

Buried under the seafloor for 86 million years, a bacterial community lives so slowly it's still surviving on a "lunch box" from dinosaur days, a new study says. (See marine-microbe pictures.)

It's been known since the 1990s that microbes can live trapped in ocean sediments for millions of years, but until now it's been a mystery how these organisms make a living.

To find out, scientists collected mud-dwelling bacteria from 11 spots, each tens of meters below the seafloor of the North Pacific Gyre, a circular current that encompasses much of the Pacific.

The gyre "just turns round and round like a huge closed pot, without exchanging much water with the rest of the ocean," said study leader Hans Røy, a geomicrobiologist at Aarhus University in Denmark.

As a result, vast swaths of ocean around the gyre—and the sediments below—are among Earth's most nutrient starved.

Probing the mud with oxygen sensors, Røy's team found that the deep-sediment bacteria are consuming oxygen at extremely sluggish rates. What's more, the team discovered the microbes are living off the same supply of organic carbon that got trapped along with them.

"They left the surface world when the dinosaurs walked the planet—and they are still eating the same lunch box that they got back then," Røy said.

And they're not alone: Such microbes may be the most common organisms on the planet, making up about 90 percent of Earth's single-celled life, recent research suggests.

Deep-Sea Bacteria Hard to Decode

Scientists don't know much about these deep-seafloor bacteria—they can't even be named yet, since their DNA doesn't match that of any known bacterial species, Røy said.

It's like having a set of fingerprints form a crime scene but no others to compare it to, he said. At the genetic level, the deep bacteria "don't look like anyone we know, so it limits the usefulness of DNA work."

Further complicating matters, in the lab "we're not able to cultivate the majority of the organisms" found deep under the seafloor, said marine microbiologist Danny Ionescu, who wasn't involved in the new study.

"Very often we're trying to overfeed them [when] they're used to poor conditions," said Ionescu, of the Max Planck Institute in Germany.

Because the organisms are so deprived, they've also adapted to reproduce very slowly, unlike other bacterial species, many of which multiply by the millions within a few days.

By contrast, trying to grow deep-sea bacteria in a petri dish is like "looking at a tree to see if it grows," said study leader Røy said, whose team's work will be published Friday in the journal Science.

Life in Slow Motion

Luckily, it wasn't hard to figure out the life spans of North Pacific Gyre bacteria. "Nature made the experiment for us," Røy said.

For starters, it's easy to determine the ages of mud layers under the North Pacific Gyre, since sediments there accumulate very slowly—about a millimeter every thousand years.

The team used their oxygen sensors to determine how much oxygen is "missing" from various sediment layers due to bacteria using the gas.

"It's a simple calculation—measuring what oxygen got in, compared with what didn't get out."

From that data, the scientists determined that each of the bacteria reproduce between once every few hundred years and once every few thousand years. This doesn't break any records—many organisms, such as sponges, can live longer.

What makes the research "fascinating," Max Planck's Ionescu said, is that it shows how life can survive on so little.

The species' slow-motion lifestyle, he added, "breaches the limits of life as we know it."