Bacteria can grow under extreme gravity: study

Apr 26, 2011 by Deborah Braconnier report
Photograph of pellet of E. coli cells formed after incubation at 403,367 × g and 37 °C for 60 h. The outer diameter of the tube is 18 mm. Image (c) PNAS, doi: 10.1073/pnas.1018027108

(PhysOrg.com) -- A new study in the Proceedings of the National Academy of Sciences shows that bacteria is capable of growing under gravity more than 400,000 times that of Earth and gives evidence that the theory of panspermia could be possible.

Biologist Shigeru Deguchi of the Japan Agency for Marine-Earth Science and Technology led the research. With his team, he set out to test the growth capability of bacteria under intense gravity conditions. With the use of a machine called an ultracentrifuge, they spun four different species of bacteria in a way to replicate hyper-gravity.

While the bacteria clumped together in pellet form when the gravity increased, their growth rate was not affected. Two of the species, Paracoccus dentrificans (soil bacteria) and were able to continue growth within a gravity rate of 403,627 g.

Researchers believe that the reason the microbes are not affected is due to their size and structure. The smaller an organism is the less sensitive it is to gravitational forces. Bacteria, a prokaryotic cell, do not have organelles. Organelles, such as cell nuclei, tend to compact and are subject to sedimentation effect and shutting down. Bacteria, by contrast, do not suffer with this problem. Researchers are still unclear as to why some are more resistant than others and say further study is needed.

The theory of panspermia believes that life on Earth could have begun when comets or asteroids carrying microbes collided with Earth. While there is no proof that microbes here are descendants from , it is now a possible theory. This research however does allow for expansion into areas where we previously thought life would not be possible. For example, the on a brown dwarf has been estimated at around 10 to 100 g. While it wasn’t believed that could grow under those conditions, this study shows that is not the case.

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More information: Microbial growth at hyperaccelerations up to 403,627 × g, PNAS, Published online before print April 25, 2011, doi:10.1073/pnas.1018027108

Abstract
It is well known that prokaryotic life can withstand extremes of temperature, pH, pressure, and radiation. Little is known about the proliferation of prokaryotic life under conditions of hyperacceleration attributable to extreme gravity, however. We found that living organisms can be surprisingly proliferative during hyperacceleration. In tests reported here, a variety of microorganisms, including Gram-negative Escherichia coli, Paracoccus denitrificans, and Shewanella amazonensis; Gram-positive Lactobacillus delbrueckii; and eukaryotic Saccharomyces cerevisiae, were cultured while being subjected to hyperaccelerative conditions. We observed and quantified robust cellular growth in these cultures across a wide range of hyperacceleration values. Most notably, the organisms P. denitrificans and E. coli were able to proliferate even at 403,627 × g. Analysis shows that the small size of prokaryotic cells is essential for their proliferation under conditions of hyperacceleration. Our results indicate that microorganisms cannot only survive during hyperacceleration but can display such robust proliferative behavior that the habitability of extraterrestrial environments must not be limited by gravity.

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that_guy
4.3 / 5 (7) Apr 26, 2011
For Rocky planets like ours, current thinking is that the larger the planet, the higher chance of plate techtonics (Which helped give early life chemicals it needed) and protective magnetic fields form - With significant supportive experimental evidence for it.

This goes to show that life should be relatively unnaffected by 2-3 g's on these planets...meaning that 'super-earths' are now a very attractive place to look for life.
sigfpe
4 / 5 (4) Apr 26, 2011
"...and gives evidence that the theory of panspermia could be possible."

I assure you, a theory of panspermia is quite possible. In fact, entire books have been written about the theory. Let us know when there's some evidence that the theory is true.
Mercury_01
5 / 5 (5) Apr 26, 2011
I cant see why anyone would have ever thought that bacteria coudnt grow under 10 - 100 g. It just doesnt seem like a logical assumption. 400,000 g is pretty impressive though, and I wouldnt have guessed that one. My question now is what would a multicellular organism look like on a planet with 10 - 100 g?
Bog_Mire
5 / 5 (9) Apr 26, 2011
My question now is what would a multicellular organism look like on a planet with 10 - 100 g?


Flat.
axemaster
not rated yet Apr 26, 2011
My question now is what would a multicellular organism look like on a planet with 10 - 100 g?


I doubt you would see land based creatures much larger than a small mouse. In all likelyhood most of the creatures would be aquatic, using equilibrium to abate the effects of gravity. But that's just a guess.
jsn3604
5 / 5 (1) Apr 26, 2011
Where did the asteroid microbes come from?
Graeme
not rated yet Apr 26, 2011
The gravity feat is more impressive that the bacteria actually grow and not just survive.

On a side track What is the highest pressure that bacteria can grow in? I believe it is over 1000 atmospheres but is there a known limit?
210
1 / 5 (5) Apr 27, 2011
Hmmm...Mega-gravity on Jupiter,after travelling at space-normal speed or mach 333 for a million years, near absolute zero and in a vacuum, bombarded by everything in the EM spectrum, and no organelles:
ANDROMEDA- no amino acids, no DNA, crystalline life that uses compartments rather than organs for biochemical synthesis. Ooops, Andromeda "...used everything and wasted nothing.." no evident mechanism for adaptive evolution, since instead of mutating it would eat the adaptive trigger, heat, cosmic rays, stray x-rays, etc, and grow forever. Shucks, back to the lab Pinky!
-word-to-ya-muthas-
Jaeherys
not rated yet Apr 27, 2011
Say what?
antialias
5 / 5 (2) Apr 27, 2011
He's referring to the SciFi novel "The Andromeda Strain" by Michael Crichton.
CreepyD
not rated yet Apr 27, 2011
What exactly are "hyperaccelerative conditions"?
Google doesn't seem to know the answer to this one..
chthonic
4 / 5 (2) Apr 27, 2011
Why investigate bacterial growth in a 403,627g environment? "Because it's there"? I expected the article to say something like, "We were trying to see whether bacteria could survive the high-acceleration impact from riding in on a asteroid or comet to a host planet." But what range of decelerations does an exoplanetary body impacting a planet sustain? And wouldn't heat be a bigger threat to destroy any exoplanetary bacteria arriving by impact? This result to me sounds like an answer in search of a research question.
antialias
5 / 5 (2) Apr 27, 2011
But what range of decelerations does an exoplanetary body impacting a planet sustain?

I don't have figures for that, but a harddrive falling on a stone floor experiences up to 30000g at the moment of impact. Given that a meteorite might be a bit faster than a falling harrdrive I could well believe that the impact accelerations might be an order of magnitude greater.
Bigblumpkin36
5 / 5 (5) Apr 27, 2011
I can't wait till we find life on exo-planets, maybe then this royal wedding will end.
Bigblumpkin36
not rated yet Apr 27, 2011
Does anyone think that aliens sent an impact rock to earth for an experiment to see if life could happen beyond (their) system? Just a dumb question, but you never no. Humans could be some little girls science project gone absurd. What do i know though?
WhiteJim
1 / 5 (5) Apr 27, 2011
All life forms we have discovered so far is related and can be traced back to a single life form. We have not found any alien life on Earth. This tells us that creating life from nothing is not easy and is very rare. Otherwise we shoud have different examples on earth of life that developed independantly. The conclusion is that life on earth must be of alien origin and the earth was seeded from life that spontaniously generated on some other planet and brought here through the scratering of astroids and comets and related events. To suggest that this planet out of the trillions of planets and dust particles that life can be on, in our galaxy was the only one to generate life spontaniously is only a religion and cannot be based on scientific thought. If life generated spntaniously here and elsewhere then we would have evidence of different unrelated life on earth from the actions of the astroids, comets, and all the churnings going on for the billions of years of our gallaxies existence
Skeptic_Heretic
4.5 / 5 (2) Apr 27, 2011
I just got a fantastic idea for materials research, unfortunately I'm not sure if we have the technological ability as of yet.

Imagine the structures these bacteria would evolve over time under such high gravity. Very well could discover some novel processes by which one could create biological supermaterials.
Bigblumpkin36
5 / 5 (1) Apr 27, 2011
Way to bring up the religion card buddy, this is physics
that_guy
5 / 5 (1) Apr 27, 2011
And wouldn't heat be a bigger threat to destroy any exoplanetary bacteria arriving by impact? This result to me sounds like an answer in search of a research question.


Yes, heat is now the biggest hazard to panspermia, especially based on the high g's that we now know that bacteria can handle. However, that question has been worked on too, and if the bacteria have a spot deep enough in the rock, they are protected to the point where it is very viable. In small asteroids (say, less than 10 feet across), they don't need to be very deep at all.

That said, I'm not a proponent of panspermia. I think it's certainly possible in small scale scenerios, but becomes very unlikely outside of a single star system - It is only slightly better than a pure acedemic question - at least it does give us something to look for on asteroids and such.
frajo
5 / 5 (4) Apr 27, 2011
All life forms we have discovered so far is related and can be traced back to a single life form. We have not found any alien life on Earth. This tells us that creating life from nothing is not easy and is very rare. Otherwise we shoud have different examples on earth of life that developed independantly.
Not really. Life on this planet, i.e. the biosphere is the result of countless years of competition and cooperation. While most early forms of life didn't make it to the present day there were some that became integrated and amalgameted and survived the rest (which might have been quite different). The biology of the first billion years on the local planet is not very well known.
sender
not rated yet Apr 27, 2011
The density yield of molecular compound production might be better from such bacteria.
Skeptic_Heretic
5 / 5 (4) Apr 27, 2011
Not really. Life on this planet, i.e. the biosphere is the result of countless years of competition and cooperation. While most early forms of life didn't make it to the present day there were some that became integrated and amalgameted and survived the rest (which might have been quite different). The biology of the first billion years on the local planet is not very well known.
Couple this with the propesity for horizontal gene transfer in single celled organisms and attempting to find the origin of life on Earth becomes highly complex.

There very well could have been hundreds of starts to life that transferred genetic material to each other resulting in a single ancestor for all of life, without that ancestor being the original life form.
The conclusion is that life on earth must be of alien origin
Right, right, because originating elsewhere averts all the challenges of creating life here and introduces no new challenges.../sarcasm
Mercury_01
not rated yet Apr 27, 2011
My question now is what would a multicellular organism look like on a planet with 10 - 100 g?


I doubt you would see land based creatures much larger than a small mouse. In all likelyhood most of the creatures would be aquatic, using equilibrium to abate the effects of gravity. But that's just a guess.


Im picturing something like a groundhog, but with legs proportioned more like a rhinoceros. I picked up a prairie dog once, and was surprised at how stalwart and muscular it was. It tried to burrow under me as I sat on the floor, and was able to wedge itself right under 80% of my mass! Its not a huge stretch for me to imagine a 10 pound rodent like that being redesigned to carry 10 times the weight. It's bones would have to be pretty thick, and it might even have some kind of exoskeleton as well that would support it's organs. Just using my imagination, Id bet that under 10g, dog- sized creatures might be the maximum size reached. Thick, anklyosaur- like dogs.
Beard
not rated yet Apr 28, 2011
The largest land animals on our planet were giant sauropods (the largest possibly being 150-200 tons and 200 feet long). A 10g world inhabited with life using earthly biology can then be expected to reach dimensions around 1/2 of that, with masses being around 1/8.

If the organisms on the 10g world are selected for size and use exotic biology, it might be beyond our imagination.
antialias
5 / 5 (1) Apr 28, 2011
All life forms we have discovered so far is related and can be traced back to a single life form. We have not found any alien life on Earth.

The question is: Did that forst life form originate here? That is as of yet unanswerable. We'll know when we detect life elsewhere.

Otherwise we shoud have different examples on earth of life that developed independantly.

No. Evolution would take care of that pretty quickly if one type is better at gathering resources than any other. Once one type gains enough of a head start in the evolutionary game then it's increasingly unlikely that a 'new start' would provide an alternative that doesn't die out immediately thereafter.

then we would have evidence of different unrelated life on earth from the actions of the astroids, comets,

since we haven't looked at too man of these (and the vast majority of them would be of non-planetary origin or have undergone conditions that would preclude life) that conclusion is a BIT premature.
that_guy
not rated yet Apr 28, 2011
The largest land animals on our planet were giant sauropods (the largest possibly being 150-200 tons and 200 feet long). A 10g world inhabited with life using earthly biology can then be expected to reach dimensions around 1/2 of that, with masses being around 1/8.

If the organisms on the 10g world are selected for size and use exotic biology, it might be beyond our imagination.


He's got a good point there. I'm sure there is a point where gravity becomes an overriding factor, but based on our own biosphere and history, it seems to indicate that bouancy or thickness of the medium(IE - look at the oceans, and the blue whale) and the oxygen content or analogue (IE look at the dinosaurs sizes) will probably have more effect on animal size than a few G's.
that_guy
5 / 5 (1) Apr 28, 2011
oh, and the largest animal known to have lived is in fact the blue whale
Mercury_01
5 / 5 (1) Apr 28, 2011
oh, and the largest animal known to have lived is in fact the blue whale


You've just made me realize that I want to see one before I die.
WhiteJim
1 / 5 (5) Apr 29, 2011
If so then why do we not see different forms of life that have been generated recently? Why can't we get life to arise from non-life in a lab? If the reason all life is the same today is because of evolution and competition then where is the new life? It is much easier to create new life today with all the organic material available to work with than there was billions of years ago.

I conclude that because we cannot find any different kind of life it implies that it is very difficult to create and that it is more likely to have been created elsewhere and gotten here that to have been created here.
Skeptic_Heretic
5 / 5 (1) Apr 29, 2011
If so then why do we not see different forms of life that have been generated recently?
Have you combed the entirety of the surface, atmosphere and terrasphere of the planet each second of each day?
Why can't we get life to arise from non-life in a lab?
We have. We commonly assemble and on occasion "evolve" RNA machines to do autonomic work for us in the lab. We've also created a functional self replicating DNA chain.
If the reason all life is the same today is because of evolution and competition then where is the new life?
Eaten most likely.
It is much easier to create new life today with all the organic material available to work with than there was billions of years ago.
There is no more or less organic material on the planet today than there was previously, beyond that, life need not be constrained to organic molecules.
frajo
5 / 5 (1) Apr 29, 2011
Why can't we get life to arise from non-life in a lab?
Yes, we can. But the experiment will take at least one milion years.
jsn3604
5 / 5 (1) Apr 29, 2011
Why can't we get life to arise from non-life in a lab?
Yes, we can. But the experiment will take at least one milion years.


In theory :-)
Quantum_Conundrum
not rated yet Apr 30, 2011
In the past, when calculating the maximum size of a tree transplanted on another planet, and assuming wind is similar to earth, but gravity is not, I found that as gravity decreases, the maximum breaking mass of a tree branch increased by a formula related by the power of 1.5. Pruning allows you to get numbers better than 1.5 in the short term, but never better than 2.0. Conversely, if you increase gravity then the maximum breaking mass of the branch decreases by a formula related by the power of 1.5.

Applying this knowledge, and assuming our redwoods are at or very near their upper height and mass limits, then the maximum height of an Earth biology tree on a planet with 10g gravity should be roughly 12 to 13ft before it breaks under it's own weight, assuming otherwise Earth-like conditions and Earth-like winds.

On the other hand, under 0.1g, a tree the size of the Avatar tree should theoretically be possible with earth-like biology and no pruning.
Quantum_Conundrum
not rated yet Apr 30, 2011
The previous post only considers gravity and hte structural integrity of wood. It disregards other environmental consequences, and also does not consider the energy transport costs of moving water up the tree trunk under extreme gravity, although under lower gravity this should clearly benefit the tree geometrically, it's unclear what the effects would be under heavy gravity, since the maximum height is much lower anyway, as the water doesn't need to be moved as far...

Additionally, for heavy gravity, this does not consider the possibility of "trees" which become much wider than they are tall, and therefore may exceed this maximum height just by becoming some sort of "mound" of tree or tree-like material, although the lower portions of the organism may still become crushed under it's own weight, destroying the cellular life there, so it might not be possible anyway. The tree may become some sort of coral-like structure building mounds on it's own dead cells.
Quantum_Conundrum
not rated yet Apr 30, 2011
The maximum height of a giraffe or sauropod like organism on an extreme gravity planet would be related by a similar formula, since the organisms tail or especially neck would break under it's own weight according to a very similar formula. Mass goes proportional to cross-sectional area and length. Weight is a consequence of mass and gravity, but since maximum strength of the neck goes up as the area of the cross-section of neck, while mass goes up by the same amount multiplied by length...

Assuming Sauropods are at or very near the maximum size for an animal on Earth. Then the maximum height of an earth-like animal on a 10g planet would be much less than the linear figure of a factor of 10 might suggest. It is again smaller by a factor of around 31, or 10^1.5. Probably around a foot in height, and maybe 1.5 to 3 feet in length head to tail.

Basicly the size of a small cat or dog would be the upper limit, and these would be the "giants" of the planet.
Beard
not rated yet Apr 30, 2011
Assuming Sauropods are at or very near the maximum size for an animal on Earth. Then the maximum height of an earth-like animal on a 10g planet would be much less than the linear figure of a factor of 10 might suggest. It is again smaller by a factor of around 31, or 10^1.5. Probably around a foot in height, and maybe 1.5 to 3 feet in length head to tail.


Why wouldn't a sauropod like creature on an 8g world with 1/2 the area and 1/8 the volume be equivalent to the ones we had on earth in terms of structural stability?
KillerKopy
1 / 5 (5) Apr 30, 2011
Can we stick to facts and not crazy theories of panspermia. Even if aliens existed(though they do not) that would still not answer the question, where everything came from.
Jim1138
1 / 5 (1) May 01, 2011
Does this mean that we should start searching for life on neutron stars, sterilize our centrifuges or chuck another paper in the trash?
Bog_Mire
not rated yet May 01, 2011
Do the right thing and recycle the paper.
Quantum_Conundrum
not rated yet May 01, 2011
Assuming Sauropods are at or very near the maximum size for an animal on Earth. Then the maximum height of an earth-like animal on a 10g planet would be much less than the linear figure of a factor of 10 might suggest. It is again smaller by a factor of around 31, or 10^1.5. Probably around a foot in height, and maybe 1.5 to 3 feet in length head to tail.


Why wouldn't a sauropod like creature on an 8g world with 1/2 the area and 1/8 the volume be equivalent to the ones we had on earth in terms of structural stability?


The strength of a material does not "scale". At a certain point, adding more bone increases the weight more than it increases the strength.

Wood and bone grow more in total strength as cross sectional area increases, yes, but their strength per unit area remains the same.

So mass (and consequently weight) increases by a cubic function with volume, but the strength of wood or bones increases by a square function with the cross sectional area.
Quantum_Conundrum
not rated yet May 01, 2011
Ok, the logic of how it becomes a power of 1.5 is a bit hard to see, but you have to think about the strength of the structure as it grows.

As long as the breaking weight is greater than the current weight, then there is still theoretical room for growth. As the structure grows, the breaking weight increases because the cross section increases. A tree can only grow taller if it continues to grow thicker.

It's easier to see going from Earth gravity to weaker gravity. If you take a tree that is at it's breaking weight when it's mass equals M, and magically transport it to a moon with 0.1g gravity, then initially, it has room to grow to a mass of 10M. However, by the time it reaches mass 10M, the trunk and primary branches are, on average, 4.64 times as large in cross-section, so therefore they can now support a mass of 46.4M...but by the time the tree gets to mass 46.4M, the trunk and primary branches reach a cross-section even bigger...
Quantum_Conundrum
not rated yet May 01, 2011
The limit of height, H, on the second world ends up being expressed as the reciprocal of gravity in terms of Earth gravity (1/XG), raised to the power 1.5, and then multiplied by the height, h, of the organism on Earth.

h*(1/(Xg))^1.5 = H

The reason for this is life doesn't grow magically. You need time for the cross-section to grow so strength exceeds what the breaking weight will be when the structure is completely grown.
J-n
5 / 5 (1) May 02, 2011
All of this pseudo-science math gives me a headache.