Live Slow, Die Old

Ancient bacteria living in deep-sea sediments are alive—but with metabolisms so slow that it’s hard to tell.

By | May 17, 2012

image: Live Slow, Die Old Deep-sea sediment bacteriaShelly Carpenter, NOAA Ocean Explorer

Deep-sea sediment bacteriaSHELLY CARPENTER, NOAA OCEAN EXPLORER

In the northern Pacific Ocean, buried 20 meters below the ocean floor, are bacteria that live life in the extreme slow lane. They have not received any fresh sources of food since they were buried 86 million years ago, when dinosaurs still walked the land. Still, they cling to life by using up the little oxygen available to them at an incredibly slow rate.

“Their activity is so slow that on our timescale, nothing happens at all,” said Hans Røy from Aarhus University, who discovered the microbes. “It’s much less than any laboratory culture we have.”

“Besides being interesting on its own, it has large implication for the potential of life in other low energy environments such as the subsurface of Mars,” added Arthur Spivack from the University of Rhode Island, who was not involved in the study.

The study, published today (May 17) in Science, is part of Røy’s ongoing effort to understand the organisms that live in marine sediments, which could account for 90 percent of all microbes in the world. “We’re looking at the most common forms of life on this planet, and we know almost nothing about them,” said Røy.

Extremely slow-going bacteria were discovered in the surface of the ocean floor in the 1990s, but many scientists initially dismissed them as dead. A Japanese group challenged that idea last year, when they showed that cells buried in sediments from the Sea of Japan could grow if they were given a fresh source of nutrients. Now, Røy has gone one step further by measuring the metabolism of subsurface bacteria in their native soil, and confirming that they are alive, if barely so.

The team collected the buried microbes on a research cruise that sailed west along the Equator from the Galapagos Islands, before turning north into a rotating collection of currents called the North Pacific Gyre. At nine stops along the way, the researchers drilled into the ocean floor to collect cylinders of sediment, 28 meters deep.

Oxygen levels typically peter out within a few centimeters of the sea floor. But Røy found that sediments beneath the gyre contained oxygen at record-breaking depths of 30 meters or more, because they settle so slowly. “If a grain sits on top of the surface, it will take a thousand years for something to sit on top of it,” he said. By the time new grains are buried, they have been stripped off all possible nutrients by surface microbes, leaving any organisms below with very little to eat. As a result, subsurface microbes maintain incredibly slow metabolisms, using up little of the buried oxygen.

By probing the sediments with needle-shaped oxygen sensors, Røy calculated that each of the deepest bacteria used up just 0.001 femtomoles of oxygen per day. To put that into perspective, if you put sediment from the North Sea into a sealed container, the microbes inside would use up all the oxygen in a few minutes. “If we did the same thing with our sediments, it would be 1,000 years before we could even measure a change,” said Røy.

"This adds to the growing evidence that sub-seafloor [microbes] survive on remarkably low energy flux and are very different from the live-fast-die-young microbes in near surface environments or laboratory cultures,” said John Parkes from Cardiff University.

Parkes also thinks Røy’s estimate may be generous. The technique the researchers used likely missed some of the cells in the sediment, undercounting the population. “The metabolism per cell is likely to be even lower!” Parkes said.

These microbes may be idling close to the minimum limit for life. They produce so little energy that they cannot even turn the whip-like flagella that allow them to move.

It is not clear how the bacteria manage with so little oxygen. “We have no clue about that at all,” said Røy. And it will be a difficult mystery to solve, especially since most of the current knowledge about microbes comes from studying them in fast-growing cultures, he added. “The very method we use to study them excludes any knowledge about something that grows this slowly.”

Another mystery revolves around the age of the cells that Røy found. They must be at least a thousand years old, but they could be much older. “If they grow this slowly and they’re still alive, then they’re also not dying very fast,” said Røy.

H. Røy et al., “Aerobic microbial respiration in 86-million-year-old deep-sea red clay,” Science doi:10.1126/science.1219424, 2012.

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Comments

Avatar of: Buzz Dengue

Buzz Dengue

Posts: 1

May 17, 2012

Where is Richard Fleischer when you need him???

Avatar of: William Tatum

William Tatum

Posts: 1

May 17, 2012

I really hope that this research gets shared with the research groups that are working on "human hibernation" for long term space travel. If we can figure out how they are slowing their metabolisms down that much without dying there might be a way to induce a similar state in a sedated human such that they could survive a journey to the nearest star or even to dramatically reduce the costs of intrastellar flights because the passengers would use up dramatically less resources and would be able to be "shipped" more efficiently. 

Avatar of: gfish3000

gfish3000

Posts: 1

May 18, 2012

One would think that but these bacteria are likely to be so radically different from us that unless we re-engineer ourselves on a molecular level, it would be very difficult to apply anything we learn to ourselves. But there is research into how to induce hibernation in humans to extend the time a stroke victim or a trauma patient has between being transported to a hospital and getting treatment. In those cases, a few minutes can mean the difference between life and death so putting parts of their metabolism in slow motion could buy as much as a few hours at best.

My vote for the "easiest" way to survive an interstellar journey is drastic robotic augmentation and genetic engineering through siRNA and specially modified viruses. Sedation over years, if not centuries, could be lethal all on its own as muscles would atrophy to dangerous extremes. We'd want our astronauts to be able to walk on worlds around other stars when they get there rather than spend months slowly re-training their muscles to work without getting a heart attack after 10 or 20 ro 100 years of it beating once a minute or something like that...

Avatar of: Sydney Von Arx

Sydney Von Arx

Posts: 2

May 18, 2012

Well, I think this article has interesting points, but personally I think William Tatum has the right idea. Instead of going "Look, cool slow growing bacteria that we will spend millions on and do nothing with", they should come up with ways to use them. I have some ideas of things they can be used for, imagine if they possessed the key to electronic devices that used way less power... or even more ambitious, the key to making artificial life.

Avatar of: rameshraghuvanshi

rameshraghuvanshi

Posts: 20

May 18, 2012

For whom  this massage you want convey?  Is it possible for man live slow and die old ?We are living most competitive era,If I  some minuet ideally I  am restless this competitive life  push you forward and forward.Another question is how much old age man alive 80/90 After 80most man became helpless  cannot do their routine  movement also.Is this kind living worth to live?I must man die right time  but it is not our hand  when to die till I think  vegetable life is not worth living

Avatar of: mscoyote

mscoyote

Posts: 7

May 18, 2012

Maybe the new perspective on how life works and some of the little feedback mechanisms life on earth has hidden are useful enough without all the over cleverness.  What is useful is understanding how to survive the next eon in company with the rest of the living organisms we share this world with.

Avatar of: Maxitom

Maxitom

Posts: 1

May 18, 2012

What about DNA repair under these circumstances?

Avatar of: Sereres Johnston

Sereres Johnston

Posts: 1

May 19, 2012

WOW!  So these cells are respirating oxygen...  but using less than seven molecules a second?  I guess is that O2, so maybe 14 atoms?  Except that there might be an undercount of cells... so they may be using even *less* than that!!?  Astonishing.

Avatar of: mightythor

mightythor

Posts: 1457

May 21, 2012

"Funding is requested for a period of 1000 years...."

Avatar of: wtanksleyjr

wtanksleyjr

Posts: 1

June 14, 2012

 OK, here's a twenty. That'll do for 1000 years, right?

Avatar of: Charles Hill

Charles Hill

Posts: 1457

June 29, 2012

Invested correctly, it might.

Avatar of: Jocelyn ZHOU

Jocelyn ZHOU

Posts: 1457

June 30, 2012

eh...be tiny, then "live slow" to "die old", this is bacteria

Avatar of: sciencegrad

sciencegrad

Posts: 1

January 7, 2013

Where does he get "86 million years?" ... At threshold sedimentation rates of 1 millimeter per 1000 years... ? How could we possibly know (who measured over 1000 years?) A) that sediment accumulates at 1 ml/ thousand years... and B) the sea floor has not been disturbed for 86 million years?!

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