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The science of deep earth biology has taken off in recent years. There are entire ecosystems which do not depend on the sun for energy - examples include the famous chemolithotrophic thermal vent bacteria, which use for energy the sulfur compounds emitted as well as the recently discovered bacteria
which react water and basalt for energy. Basically any chemical reaction which can occur in a living cell has been harnessed by some species of bacterium to provide energy.
Bacteria have been very good at exploiting energy sources. I theorize that there must be bacteria in the deep earth which use heat differentials to generate energy. Microenvironments with large, stable heat differentials are probably very common in the deep earth, where cooler fluids moving downwards encounter warmer rocks heated from below. One can imagine that a biofilm on a warm rock with cool fluid moving by could run endothermic reactions on this differential, using the heat to catalyze an energy producing reaction (generation of ATP), then regenerating the components of this reaction on the cool side.
These organisms would be difficult to isolate. Common culture techniques do not create temperature differentials of this sort, and so these organisms could not grow. PCR experiments on soil have demonstrated that many more species exist in the soil than can be cultured - the demonstration that unique ribosomes can be found does not tell you much about the organism, though.
One way to track these things down and create a culture environment to grow them might be a deduce what sort of reaction they might use to harness heat energy. A clue is the presence of huge stores of liquid oil. The origin of oil is still controversial - possibly it is actively generated by deep earth ecosystems. My knowledge of organic/inorganic chemistry is too limited to propose specific reactions - the likely candidate would be an endothermic reaction which generates long chain alkanes as a final product (as our metabolism generates CO2 + H20).
One might ask - who cares if there are pyrolithotrophs? For one, the possibility of huge, unknown ecosystems in the earth is (to me) as exciting as the existence of unknown ecosystems on other planets. For two, an awareness of the various forms life might take is necessary if we are to identify life on other planets - which might be very different than it is here. For three, if our oil is being actively generated by a live ecosystems, it would be prudent to understand and protect it at least - and possibly even cultivate it!
Metabolic diversity
http://cwx.prenhall...deluxe-content.html
[bungston, Oct 04 2004, last modified Oct 06 2004]
(?) The deep, hot earth.
http://people.corne...pages/tg21/DHB.html
Thomas Gold's theories on petrochemical generation. [bungston, Oct 04 2004, last modified Oct 06 2004]
(?) Deep, hot temperature gradients!
http://www.gsfc.nas...e/2001/11-09-00.htm
(Apparently our government favors the overuse of exclamation points.) [DrCurry, Oct 04 2004, last modified Oct 06 2004]
(?) Molecular microbial ecology
http://www.eastman....rob/mol%20ecol.html
This overview is the best I could find on molecular microbial ecology. Interestingly, these folks are dentists studying the mouth. But the same principles apply to soil ecology - or petrochemical ecology. [bungston, Oct 04 2004, last modified Oct 06 2004]
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The animals living on the deep sea thermal vents already experience colossal temperature gradients along their lengths. Surely if there are bacteria that use this as an energy source, they will more easily be found round these vents? |
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You are absolutely right. It seemed to me that these sorts of environments may be rather action-packed, and the pyrotrophs might be outcompeted or eaten by animals with more conventional metabolisms. However, if you posit there are teeming microbial communities in the deep earth with pyrotrophs serving as the basis, there would not doubt be predators etc there as well. But the point is the same for the vents and the deep earth - unless you specifically look for these organisms, you will never know. |
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I thought this was already a commonly known (if generally discounted) theory. What's your idea? |
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"What is the Halfbakery?
The halfbakery is a communal database of invention and speculation. Its users can publish ideas and add links and commentary to other people's ideas. " |
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As you can see, this is not an invention like a lightbulb, but rather speculation about the nature of the world and a proposal for how these things might be further investigated - along the lines of Vernon's "Gravity Waves" idea. Because I suspected there might be comments such as these, the last paragraph states why these matters might be important. I did notice that the exotic biology topics previously posted on the HB were mostly of the little green men variety. |
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Folks, as far as I know the concept of pyrotrophs is original with me. The idea is not that there are deep bacteria or that they make oil, but that these bacteria might be able to use heat as an energy source, the way plants use the sun. I did search the web before posting. If you two are familiar with pyrotrophs discussions elsewhere I would much like to read them - please post the links for my edification and I will delete the idea. |
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10 degrees doubles a typical k rate of reaction
There are lots of things with 10 degrees difference between a few inches. Maybe there are trees that use this temp difference. |
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I have been mulling over petrochemicals and oil, a result of recent discussions about biodiesel. I was pondering again the origin of oil and natural gas. Coal seems to pretty clearly be from peat bogs. But oil? |
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I propose that oil is generated from beds of limestone and other carbonate minerals by pyrolithotrophs. The carbonate would be the electron acceptor and would be reduced to oil and gas. The electron donor would be whatever chlorophyll analog the PyLTs use to capture heat energy. There might not be many of the PyLTs, but a bed of them atop a carbonate deposit could convert CaCO3 into CH4 and other alkanes over millions of years. Several predictions can be made using this model: |
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1: Oil and gas beds should be closely associated with beds of carbonate minerals. In some instances, of course, the carbonates will have all been used up and converted to oil/gas. |
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2: The calcium and magnesium from the carbonate rocks would be waste products for the PyLT organisms. As would the oxygen. Thus, the prediction would be for calcium and magnesium oxides to be found in association with petrochemical deposits. |
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3: PyLT DNA. Since DNA is hydrophilic, any analysis of oil for DNA might come up empty. However, DNA from PyLTs would be expected to concentrate in any water associated with petrochemicals. Since contaminated surface water is often pumped into oil deposits to move the oil, one would have to analyse water from a fresh, untapped oil reservoir. But this water should contain DNA from these critters. The gene for their chlorophyll analog should be different enough to stand out in sequence analogy studies. |
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Well, as a waste product, oil is pretty high-energy. It would be much more believable as an energy storage medium. Perhaps the bacteria make CH4, and the heat and pressure polymerize it, making higher energy dinner? |
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Oil is high energy in an oxidizing environment. I think it would be tough to get at that energy unless you had access to an electron acceptor like oxygen, sulfur etc. I agree that CH4 making bacteria are more elikely, since there are plenty of them known to exist. |
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At a sufficient depth, with no contact with the surface, there are probably still a bunch of organic molecules in higher energy configurations. The current theory of how all known life formed is that it happened under conditions similar to this. |
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Perhaps rather than a long lost relative, this life would be better considered an alien on our own planet, if it evolved separately from abiotic elements. If so, you shouldn't be looking for DNA, but for something really different. Indeed, the need to find cell wall components seems a little prejudicial. Under such conditions, perhaps life doesn't require compartmentalization, being simply an enzyme of some sort that casts oil as a waste product of its' simple replication? |
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