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Thread: Life beneath ocean floor

  1. #1
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    Life beneath ocean floor

    Soil beneath ocean found to harbor long lived bacteria, fungi and viruses
    Researchers with the Integrated Ocean Drilling Program (IODP) have presented findings at this year's Goldschmidt conference. They report having found bacteria, fungi and viruses living a mile and a half beneath the ocean floor—such specimens, they report, appear to be millions of years old and reproduce only every 10,000 years.

    All of the specimens found, the team reports, exist in sediment that is approximately 100 million years old, which suggests that they too may be nearly the same age.

    In addition to wondering how the microbes find an energy source, the researchers also appear perplexed as to how they reproduce with such great distances between others of their kind.
    I think this is their briefing paper(? ..I hope ..):
    We conducted gas chemistry and isotopic analyses using a new mud-gas monitoring laboratory during riser-drilling operation, which provided the first indication of biologically mediated CO2 reduction to methane at the 2 km-deep coalbed layers. The numbers of microbial cells are generally less than 103 cells cm-3; however, increase of biomass was observed at the coal layers. Potential rates of organoclastic sulfate reduction are elevated in coalbed-bearing strata.
    The slow reproduction rate, and estimated longevity at such depths are noteworthy (I think).

    That they also found 10 times more viruses than bacteria is also interesting ..
    In a competitive environment of self-replicators, the ones that replicate faster, tend to end up being more successful. In fact, they drive the slower ones to extinction. Extended and slow replicating RNA oligonucleotides, (for eg), then end up actually evolving into much shorter and more rapidly replicating entities*, so the predecessors of these specimens must have been just about completely dormant from an evolutionary viewpoint(?)

    Interesting ..

    Reference:
    * Spiegelman, S. An in vitro analysis of a replicating molecule. Am. Sci. 1967, 55, 221–264.

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    In a competitive environment of self-replicators, the ones that replicate faster, tend to end up being more successful. In fact, they drive the slower ones to extinction. Extended and slow replicating RNA oligonucleotides, (for eg), then end up actually evolving into much shorter and more rapidly replicating entities*, so the predecessors of these specimens must have been just about completely dormant from an evolutionary viewpoint(?)
    This may not be the case if the "predecessors" originated in a more favorable site and then migrated into these deeper regions that subsequently limited growth rate...

  3. #3
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    Quote Originally Posted by BioSci View Post
    This may not be the case if the "predecessors" originated in a more favorable site and then migrated into these deeper regions that subsequently limited growth rate...
    Yes, I suppose .. (admittedly I wasn't thinking of that).

    Sometimes I wonder why such life forms 'migrate' to such extreme locations(?) Clearly the bulk of life hangs out in more convenient places, so why would these things migrate? On the surface its pretty easy to think of them pursuing food/energy, or going with the flow of water. If they started out in the ocean water, then surely they would've had abundant food and water and the physical freedom to reproduce, right there. But 2.4 kms underneath the ocean floor?

    They're chemotrophs too, and it looks like they've (maybe) been there for ~100 million years or so. They were discovered in/around coal seams too, eh? Looks to me like they were probably associated with the formation of the coal(?) Perhaps they might've trapped by geological upheaval, too(?)

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    Quote Originally Posted by Selfsim View Post

    Sometimes I wonder why such life forms 'migrate' to such extreme locations(?) Clearly the bulk of life hangs out in more convenient places, so why would these things migrate? On the surface its pretty easy to think of them pursuing food/energy, or going with the flow of water. If they started out in the ocean water, then surely they would've had abundant food and water and the physical freedom to reproduce, right there. But 2.4 kms underneath the ocean floor?
    Good question. I suppose they didn't migrate like a flock of geese. Probably a variety of microbes were brought down there by some physical processes
    and then natural selection did the rest. The ones we see today are the ones that survived.

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    Quote Originally Posted by Selfsim View Post
    Yes, I suppose .. (admittedly I wasn't thinking of that).

    Sometimes I wonder why such life forms 'migrate' to such extreme locations(?) Clearly the bulk of life hangs out in more convenient places, so why would these things migrate?
    Basically, when it involves life and evolution, I like to simply remember that: "if it can happen, it likely will..."

    Bacteria do not choose where to live (other than short range movements) - rather, if life is possible, they will continue to grow and slowly spread into more marginal spaces until they can no longer grow (or are competed out by something else). If their growth is then limited by lack of nutrients, heat, cold, toxins, etc. evolution will select for phenotypes that can better survive and reproduce under such conditions.

    Such slow growth rates, as reported here, are likely close to the limits to still be considered "alive." One might even question how they are able to measure such low rates of reproduction?

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    Hmm .. I dunno ..

    If these organisms already existed prior to the formation of the surrounding coal (which would imply that they evolved prior to the Carboniferous, say during the Precambrian era), then I would think that their forebears would have been fairly prolific reproducers, (which is how the coal formed in the first place … ie from 'peat bogs' etc)?

    (The area they were found in (off the Shimokita Peninsula?) was formed by subduction of the Pacific plate .. so geological processes were definitely at play in all this also).

    So, under this scenario, their forebears were merrily reproducing, and when the surrounding environment changed, some of their metabolisms slowed, and reproduction would have had to come to an almost standstill, (as is evidenced by their now comparatively sparse distributions, and low densities). If any faster ones survived, they would've taken over the slower ones and extinction of the population, I would think, would have resulted? (This is almost a 'law' which defines the outcome of RNA oligonucleotide population replication).
    I guess the changed environment would've helped to kill off the abundant fast reproducers too, leaving small numbers of the slower ones. If the slower ones then had a slower metabolism compared with the present-day specimens, then they must been pretty close to "not living" (on two counts - metabolism and reproduction). Under this scenario, Selection on the survivors would've had a pretty hard time selecting for anything (over something else) because of the extremely slow metabolism and reproduction cycles(??)

    The migration option seems more preferable except for the fact they were found ~2km below the sea floor, in solid rock under ~1.5 kms of nutrient abundant watery ocean, so why would there be anything evolvable at those depths, in that environment at all?

    Intriguing ..

    PS: I'm pretty sure I won't get agreement on the above .. don't worry .. I'm not particularly attached to the idea … (something doesn't add up about it anyway .. )

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