Bacteria alive (more or less) in 86-million-year-old seabed clay

May 18, 2012 by Lin Edwards report
Hans Røy. Image from his page at pure.au.dk

(Phys.org) -- A new study by scientists from Denmark and Germany has found live bacteria trapped in red clay deposited on the ocean floor some 86 million years ago. The bacteria use miniscule amounts of oxygen and move only extremely slowly.

Researchers led by Hans Røy from the Center for Geomicrobiology at Aarhus University in Denmark, extracted samples from columns of sediment up to around 30 meters beneath the in the region of rotating currents north of Hawaii known as the North Pacific Gyre. The sediment columns, built up by deposition of clay, dead algae and crustaceans, and dust, can be as much as several kilometres thick, with the most ancient sediment at the bottom of the columns.

The team used sensitive sensors to measure the oxygen concentration in the sediment cores. Knowing how much oxygen should have been present at each level allowed them to determine if oxygen was “missing,” which meant it had been consumed by microbes. In most regions of seabed examined previously, all the oxygen is consumed within the first 10 cm of sediment.

They discovered that within the clay were slowly using the oxygen, and remained alive even at a depth of around 30 meters, even though they have not had access to fresh organic matter for millions of years.

Oxygen respiration rates at the sediment-water interface were 10 μM per liter of sediment per year, and dropped to 0.001 μM at 30 meters, where the sediments were estimated to be 86 million years old. Cellular respiration rates also decreased with depth but stabilized at 0.001 femtomoles of oxygen per cell per day at 1.10 meters beneath the sea floor. (A femtomole is a billionth of a millionth of a mole.) Røy said the team had “no clue” how the microbes were able to subsist on so little oxygen.

Dr. Røy’s team estimated the turnover of the bacterial biomass would take from a few hundred to a few thousand years, but the turnover could represent cell repair rather than cell division. The bacteria may be operating on the absolute minimum energy requirement, which is just sufficient to keep their DNA and enzymes working, and to maintain an electric potential across their cell membranes.

The activity of the bacteria is so slow that Røy likened it to staring at a tree to watch it grow taller, and said the team did not know if the bacteria were reproducing, or if they were the same bacteria that had been deposited in the sediment and were “just not dying.” He estimated they must be at least 1000 years old, but could be much older. They have no contact with sunlight or the surface.

Røy said that an estimated 90 percent of the Earth’s microbial life may exist under the sea floor, but studying them was difficult because the methods have been developed in studying bacteria with rapid life-cycles.

Dr Røy said similar life forms could exist on other planets; if microbial life had ever existed, they could remain alive even if cut off from the surface for millions of years. He also said it gave him a greater appreciation of life on Earth, that you can store clay on the bottom of the sea for 86 million years and find that “somebody’s still living in it.”

Explore further: Nitrous oxide from ocean microbes

More information: Aerobic Microbial Respiration in 86-Million-Year-Old Deep-Sea Red Clay, Science 18 May 2012: Vol. 336 no. 6083 pp. 922-925. DOI: 10.1126/science.1219424

ABSTRACT
Microbial communities can subsist at depth in marine sediments without fresh supply of organic matter for millions of years. At threshold sedimentation rates of 1 millimeter per 1000 years, the low rates of microbial community metabolism in the North Pacific Gyre allow sediments to remain oxygenated tens of meters below the sea floor. We found that the oxygen respiration rates dropped from 10 micromoles of O2 liter−1 year−1 near the sediment-water interface to 0.001 micromoles of O2 liter−1 year−1 at 30-meter depth within 86 million-year-old sediment. The cell-specific respiration rate decreased with depth but stabilized at around 10−3 femtomoles of O2 cell−1 day−1 10 meters below the seafloor. This result indicated that the community size is controlled by the rate of carbon oxidation and thereby by the low available energy flux.

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gwrede
3.8 / 5 (6) May 18, 2012
(A femtomole is a billionth of a millionth of a mole.)
Duh! Another article "for the layman". But why explain femto and not mole? Could it be that the (also layman?) editor doesn't know?
ShotmanMaslo
4.7 / 5 (3) May 18, 2012
The cell-specific respiration rate decreased with depth but stabilized at around 103 femtomoles of O2 cell1 day1 10 meters below the seafloor.


10^-3 femtomoles is around 600 000 oxygen molecules per cell per day.
kevinrtrs
1.3 / 5 (32) May 18, 2012
even though they have not had access to fresh organic matter for millions of years

Do they seriously believe this to be true? How do they know that the bacteria's been entombed for that long - was someone there to document the date and time the bacteria was encased?
Did someone actually observe that the bacteria remained alive all this time?
The answer to both questions is an emphatic NO.
Which means that they are simply making non-scientific assumptions on that particular point. Has anyone anywhere else ever witnessed / observed that bacteria can live that long?
kevinrtrs
1.2 / 5 (33) May 18, 2012
He also said it gave him a greater appreciation of life on Earth, that you can store clay on the bottom of the sea for 86 million years and find that somebodys still living in it.

Which is more credible - that the 86 million years is incorrect or that the bacteria lived that long? One thing that undermines the age is that he does not show how the sediment got deposited over those supposed 86 million years. What if there was a time in the not so distant past when there was a huge amount of sediment deposition in a very short period of time? The researcher cannot rule this out, hence his 86 million years is highly questionable.
Musashi
4.6 / 5 (20) May 18, 2012
"Which is more credible(...)"

We all know the alternative you subscribe to, so you seriously lack the credibility to question "credibility". Funny how that works...
djr
4.7 / 5 (14) May 18, 2012
"Which is more credible" - I am sure the confidence in the understanding of the age of the clay is pretty high. Scientists have multiple ways of cross checking the age of materials - it is a pretty solid science - it is interesting/discouraging how many people are comfortable questioning very fundamental aspects of science.
Objectivist
4.1 / 5 (10) May 18, 2012
Which is more credible - that the 86 million years is incorrect or that the bacteria lived that long?

That the bacteria lived that long.
Lurker2358
2.4 / 5 (5) May 18, 2012
Which is more credible - that the 86 million years is incorrect or that the bacteria lived that long?

That the bacteria lived that long.


How about the obvious solution, which is that the bacteria tunneled there recently, just like any other sub-terrain organism could have.
PhotonX
3.9 / 5 (7) May 18, 2012

Duh! Another article "for the layman". But why explain femto and not mole? Could it be that the (also layman?) editor doesn't know?

It's widely known that a mole is 5 voles, or 1/3 a gopher. Or 6000 kevintards, if you believe in that measurement.
.

Then kevintrs adds:
How do they know that the bacteria's been entombed for that long - was someone there to document the date and time the bacteria was encased?

Again with the same old tired argument from ignorance. Don't you ever get tired of that? I know I do. So, how do we know the clay was laid down 6000 years ago, as you believe? Were you there to see it? How do we know it wasn't laid down yesterday?
.
Now I don't know how they arrived at the 86 Mya estimate. But...given a choice between believing the sediments are six million years old or six thousand, I'll take my chances with the scientists, thank you. Meanwhile, you've reminded me to head over to Yahoo!Answers and laugh at the R&S posters.
stun-dexim
not rated yet May 18, 2012
Okay people... a little critical reading will simply show that these "scientists" are working on NOTHING at all here but assumption. i.e. they didn't even identify that bacteria existed in those cores (aside from normal dead biomass that you would expect to see) or even identify any cellular activity ... they simply assumed that since oxygen levels are not what they expected to be.... this "meant it had been consumed by microbes". The "researchers" have to turn up something for next years funding... so this is what you get.

"The team used sensitive oxygen sensors to measure the oxygen concentration in the sediment cores. Knowing how much oxygen should have been present at each level allowed them to determine if oxygen was missing, which meant it had been consumed by microbes. In most regions of seabed examined previously, all the oxygen is consumed within the first 10 cm of sediment."

Also... do you seriously believe "all the oxygen is consumed within the first 10 cm."

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