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Multicellular Life Evolves In Months, In a Lab

Posted by Soulskill on from the selecting-for-extroverted-cells dept.

ananyo writes "The origin of multicellular life, one of the most important developments in Earth's history, could have occurred with surprising speed, U.S. researchers have shown. In the lab, a single-celled yeast (Saccharomyces cerevisiae) took less than 60 days to evolve into many-celled clusters that behaved as individuals. The clusters even developed a primitive division of labor, with some cells dying so that others could grow and reproduce. Multicellular life has evolved independently at least 25 times, but these transitions are so ancient that they have been hard to study. The researchers wanted to see if they could evolve multicellularity in a single-celled organism, using gravity as the selective pressure. In a tube of liquid, clusters of yeast cells settle at the bottom more quickly than single cells. By culturing only the cells that sank, they selected for those that stick together. After many rounds of selection over 60 days, the yeast had evolved into 'snowflakes' comprising dozens of cells."

15 of 285 comments (clear)

  1. Not so sure about this. by Anonymous Coward · · Score: 5, Informative

    This is likely just re-emergence of previously evolved and currently dormant behavior.

    1. Re:Not so sure about this. by Anonymous Coward · · Score: 5, Informative

      Also mentioned in tfa. The scientist says that he plans to do an experiment with organisms without multicellular ancestors.

    2. Re:Not so sure about this. by Anonymous Coward · · Score: 5, Informative

      This was on RichardDawkins.net back in June, and in the version of the article linked there, there were these telling paragraphs:

      Sceptics, however, point out that many yeast strains naturally form colonies, and that their ancestors were multicellular tens or hundreds of millions of years ago. As a result, they may have retained some evolved mechanisms for cell adhesion and programmed cell death, effectively stacking the deck in favour of Ratcliff's experiment.

      "I bet that yeast, having once been multicellular, never lost it completely," says Neil Blackstone, an evolutionary biologist at Northern Illinois University in DeKalb. "I don't think if you took something that had never been multicellular you would get it so quickly."

  2. I've always wondered... by Beeftopia · · Score: 5, Insightful

    Do the mechanisms which originally created life still occur? Or is "The Genesis Event" so rare that it was a one-time occurrence billions of years ago?

    1. Re:I've always wondered... by Samantha+Wright · · Score: 5, Informative

      That's a big question! We currently believe that the circumstances that created life were pretty harsh in some respects and extremely mild in others. There are a number of different ideas floating around, including the proverbial primordial soup, clouds of space dust (panspermia), and a boiling puddle of fat. Most likely, the conditions that were on Earth billions of years ago (a hot boiling hell with a mostly hydrogen atmosphere, amongst other things) contributed substantially to the factors that led to life's rise.

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    2. Re:I've always wondered... by tchuladdiass · · Score: 5, Interesting

      Now a related question -- is there any evidence (for or against) that life originated more than once on earth? Is the prevailing theory that a single reproducing organism came into being, from which all others were derived, or is it more likely that multiple instances of life happened over the course of time, and they all happen to take the same form? If this is the case, then it lends credence to life existing elsewhere in the universe, with much similarity to what we know. However, if it is unlikely for more than one independent instance of life to be similar, then we should be observing various non-related life types here on earth (i.e., some carbon based, some silicon based, etc).

    3. Re:I've always wondered... by Samantha+Wright · · Score: 5, Informative

      This has indeed been pondered! We're pretty sure that all life that presently exists all comes from one root, however. If there ever were alternative life-starting events, they didn't survive. The reason for this is that all extant organisms share a number of completely arbitrary decisions called chirality (if you know any physics, that's left-handed vs. right-handed molecular symmetry.) Chirality is completely random in the chemical reactions that produce amino acids and nucleotides, but absolutely fixed, in the same way, in every living organism we've studied. A number of environmental tests have been conducted specifically to look for organisms of contrary chirality, but we haven't found anything yet.

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
  3. Genesis by sakdoctor · · Score: 5, Funny

    God still holds the copyright for the original genesis event. It should have entered the public domain, but the copyright just keeps getting extended, and extended for billions of years. God keeps raking in the royalties and has no incentive to create new works, which is why you haven't heard anything from him lately.

  4. Relation to yeast by pgward · · Score: 5, Funny

    Reading the comments on the physorg page made by intelligent design supporters, I have come to a conclusion. Some of us have not evolved far beyond yeast.

  5. Re:Yeasty "evolution" by Samantha+Wright · · Score: 5, Insightful

    Well, it's not that hard to create a similar environment in the real world, they take too long to get grant money for. Consider, for example, a microbe growing in a hot spring that needs a very high temperature to function properly (like every molecular biologist's friend, Thermus aquaticus.) If that thing floats to the top of the pond, it might get cold and die. Evolutionary pressures such as sink-or-die aren't that implausible.

    Think of it this way: a random walk will get to every possible location eventually. If you push it in a certain direction, it'll simply get there sooner. But if it doesn't get there when you do, then there's no chance it'll ever get there on its own. Unless they tampered with the genes of the yeast in question, these results are completely legitimate.

    --
    Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
  6. Yes - sounds like "grant time" by Moblaster · · Score: 5, Insightful

    I suspect it's not "evolution" at all, but subtly bad science (i.e. a scientist gunning for more grant money). DNA can express in many ways given varying environmental conditions, without the mutations that characterize true evolution -- and artificially forcing genetic drift by selecting for the bottom-clumpers is certainly VERY DIFFERENT from having gravity serve as the "selection pressure."

    It's well known DNA can express in many different ways without true evolution. We've come a long way from the theory of Lamarckian evolutionary theory (evolution of acquired characteristics). One is example: exons, which can express differently across generations based on environmental conditions-- without actual change to the DNA.

    I'm thinking this great discovery will get pounded upon by other biologists pretty quickly -- and put in its proper place as an interesting science experiment that really does not advance the field much if at all. INTERESTING evolution would be a group of mutations that lead to a multicellular outcome. That's NOT what these guys 1) demonstrated happened (multicellular DNA base-pair-causing mutations) or 2) proved was the actual genetic cause at the molecular-biology level.

    1. Re:Yes - sounds like "grant time" by airuck · · Score: 5, Informative

      10 yeast cells clumped together have more mass than 1 yeast cell. Therefore they sink to the bottom of a tube.

      Bzzt. Please review the difference between mass and density and the relationship between density and buoyancy.

      --
      First entomology, then virology, and finally bioinformatics systems. Bugs follow me wherever I go.
    2. Re:Yes - sounds like "grant time" by Eskarel · · Score: 5, Informative

      The summary is true, but ultimately misleading.

      This is evolution, and it did happen in months. What it doesn't account for is getting the clumping gene in the first place, and that the likelihood of getting selection pressures as extreme as the ones in the lab is fairly low.

      They've proven that yeast has the capacity to evolve in this way given the right selection pressures, which is interesting. With additional research they may be able to prove that many other single celled life forms have the same capacity, from which we may extrapolate that the gene responsible for this behavior either occurred very early or is a relatively minor mutation.

      The "more quickly than we believed" part is probably bogus. They applied extreme selection pressures to this particular colony of yeast and so they got an extreme time scale result the same would happen in any species if you extrapolated for the length of a given generation. You could do the same thing to humans for some arbitrary characteristic.

    3. Re:Yes - sounds like "grant time" by robotkid · · Score: 5, Insightful

      I suspect it's not "evolution" at all, but subtly bad science (i.e. a scientist gunning for more grant money). DNA can express in many ways given varying environmental conditions, without the mutations that characterize true evolution -- and artificially forcing genetic drift by selecting for the bottom-clumpers is certainly VERY DIFFERENT from having gravity serve as the "selection pressure."

      It's well known DNA can express in many different ways without true evolution. We've come a long way from the theory of Lamarckian evolutionary theory (evolution of acquired characteristics). One is example: exons, which can express differently across generations based on environmental conditions-- without actual change to the DNA.

      I'm thinking this great discovery will get pounded upon by other biologists pretty quickly -- and put in its proper place as an interesting science experiment that really does not advance the field much if at all. INTERESTING evolution would be a group of mutations that lead to a multicellular outcome. That's NOT what these guys 1) demonstrated happened (multicellular DNA base-pair-causing mutations) or 2) proved was the actual genetic cause at the molecular-biology level.

      IAAMBP (I am a molecular biophysicist) and I actually just finished discussing this article at work before seeing it on /. The parent post is an odd mix of insightful comments and flamebait so I'll respond to the former. BTW the actual research article itself is free for everyone to read, thanks to the authors shelling out an extra 1K$ to allow public access. I'll link it below:

      http://www.pnas.org/content/early/2012/01/10/1115323109.full.pdf+html

      If you would prefer having to pay 10-30$ for the privilege of reading what your tax dollars already paid for instead of this commie "open access" stuff, please call your congressman and tell him/her to support HR bill 3699.

      To contextualize this work: the path that led from single-celled eukaryotes to multicellular organisms is one of those $64,000 questions in evolutionary biology, that weird crossover from outright competition to coordinated teamwork. The advantages of being multicellular really pay off for big, complex organisms, but why on earth would it have been advantageous for a small group of a few dozen cells? This paper does not answer the question by any stretch, but it does provide a few interesting, unexpected clues. Most groups asking this question focus on Volvocine algae, which evolved multicellularity so recently such that you can compare them side by side with their nearly identical single-celled cousins in the very same pond. But these are not the most convenient organisms to work with; they have a very complicated life cycle, and have a monster-sized genome for their diminutive size (~140 million bases) and doing genetics on such beasties is still quite difficult and tedious.

      Yeast, on the other hand, are really easy to work with and are actually pretty boring in most respects; ~12 million base pairs which have all been sequenced many times over. You can actually custom order them with any gene you want deleted just to see what happens, it's that well characterized. So the observation that artificially selecting for clusters in boring yeast leads to weird snowflake-shape colonies with something that resembles "programmed cell death" in higher organisms is completely unexpected an novel. "Programmed cell death" literally means that the colony has found a way to promote what's good for the colony over what's good for the individual, even though these are only 60 days removed from being a pretty ordinary yeast.

      Is this how it happened billions of years ago? Probably not, this is just boring yeast after all, and I can't think of a scenario where sinking to the bottom is a life-or-death advantage. In the case of the algae, it would in fact be suicidal to sink beyond where the

    4. Re:Yes - sounds like "grant time" by GauteL · · Score: 5, Interesting

      First. Thank you for a very interesting post which provides insight that is still understandable by those of us who are not molecular biophysicists. This is not always easy to do.

      I may now be able to provide some insight into Slashdot's science discussions, which you may or may not have discovered yet....

      A good scientist (which I'm sure you are) will read new research with an open mind combined with healthy scepticism. He/she won't automatically discard papers due to confirmation bias, and they won't shout "CORRELATION DOES NOT EQUAL CAUSATION" every single time they read reporting of a paper which suggests some correlation, because they realise that demonstrating correlation is often a necessary first step towards establishing causation and as such it is still novel and useful to publish papers that suggests correlation.

      Slashdot, however, is home to some brilliant scientists who are completely drowned out by the masses of cynical, semi-clever "know-it-alls" who love to demonstrate their cleverness by shooting down any new research, often without bothering to read it first. They will shout "bad science" at the top of their lungs as a knee-jerk reaction to any perceived short coming, even if this short coming is just a limitation in scope of a paper or simply just ignorance on their own part. If the paper doesn't fully answer every possible question, it is worthless.