Watching Bacteria Evolve, With Predictable Results

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If we could somehow rewind the history of life to the dawn of the animal kingdom, it would be unlikely that we humans would ever evolve, the evolutionary biologist Stephen Jay Gould argued. The history of life was shaped by too many flukes and contingencies to repeat its course.


Scientists can’t turn back the clock 700 million years, so we can’t know for sure whether Dr. Gould was right on that particular point. But in experiments using bacteria and other fast-breeding organisms, scientists can replay evolution many times over in their labs. And the results of a new experiment published Thursday in the journal Cell Reports demonstrate — with movies — that evolution can be astoundingly predictable.

The experiment was carried out by Joao Xavier of Memorial Sloan-Kettering Cancer Center and his colleagues. They studied a common species of bacteria called Pseudomonas aeruginosa. These microbes live pretty much everywhere — in dirt, in water, on our skin. Under certain conditions, they also invade our bodies and cause dangerous infections. People with cystic fibrosis, for example, can get P. aeruginosa infections in their lungs, which are often impossible to eradicate.

To better understand the biology of this pathogen, Dr. Xavier began to study how it searches for food. In a process called swarming, the bacteria spray out gooey molecules that form a slippery carpet; they can then slither over it by whipping their tails, devouring food they encounter along the way.

Written By: Carl Zimmer
continue to source article at nytimes.com

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  1. Scientists can’t turn back the clock 700 million years, so we can’t know for sure whether Dr. Gould was right

    “In this case, it could be that there are only a few solutions in the evolutionary space,” he said.

    oh dear…

    interesting article but i fear the conclusions are begging to be picked ub by those looking for “proof of design”

    while both these comments are true, this is a study of bacteria, not multi-cellular organisms. there’s no doubt that evolution can only work within parameters, and these can be predictable in lab conditions, but higher levels of complexity increase the parameters by orders of magnitude. doesn’t mean the evolution of cats is inevitable

    • In reply to #1 by SaganTheCat:

      “this is a study of bacteria, not multi-cellular organisms. there’s no doubt that evolution can only work within parameters, and these can be predictable in lab conditions, but higher levels of complexity increase the parameters by orders of magnitude. doesn’t mean the evolution of cats is inevitable”

      The set of physical parameters encountered by multicellular organisms in the ‘real world’ outside of the lab are generally quite predictable, it could be argued that the evolutionary tendency for multicellular organisms to conform to certain bodyforms and develop certain abilities and senses etc is quite inevitable in spite of their underlying high levels of biological complexity when compared with a humble species of bacteria.

      Consider recently extant marsupial predators such as Thylacoleo carnifex and Thylacinus cynocephalus and their striking similarity to multicellular organisms from other continents such as lions, tigers and wolves that evolved independently to fill similar ecological niches. Or the similarity between certain Jurassic Ichthyosaurs and some modern-day cetaceans.

      Of course this doesn’t demonstrate that the evolution of cats is inevitable, but it could point towards a certain degree of inevitability towards multicellular organisms evolving very similar characteristics, appearance and senses/abilities etc to fill certain specific ecological niches within a ‘standardised’ framework of physical parameters.

      So, if the evolution of cats is not inevitable, perhaps the evolution of something that looks remarkably similar to a cat within the same set of physical parameters and evolved to fill the same ecological niche, does have a hint of inevitability about it. Its a shame we don’t live long enough to observe this directly in the lab.

      • In reply to #6 by Steve_M:

        In reply to #1 by SaganTheCat:

        “So, if the evolution of cats is not inevitable, perhaps the evolution of something that looks remarkably similar to a cat within the same set of physical parameters and evolved to fill the same ecological niche, does have a hint of inevitability about it. Its a shame we don’t live long enough to observe this directly in the lab.

        i take your point although it’s easy to be biased when it comes to spotting similarities. the ocean was a good environment to allow a 4 legged animal to evolve into ichtyosaurus that looked like a fish, but more marine reptiles took on a very different shape like plesiosaurs and modern turtles, but these are still examples of one order of animal with a limited design space due to its skeleton. notice how invertibrates have not done a very good job of looking like mammals? ultimately the longer you give for divergence, the further appart things become. one general prediction one can assume however is; if it has to move fast enough for the viscocity of its environment to offer resistance, a bit of streamlining will happen.

        on earth animals have gone for soft bodies, hard shells or internal skeletons. there could be other options or combinations but for the right genetic mutation half a billion years ago. then look at other eukyaryotes, there are fungi and plants… the options of chloroplasts or mitochondria… (just different effects of predation/parasitism/symbiosis) many of the similarities today were set hundreds of millions of years ago. if we found multicellular life elsewhere, who’d guess at what strategies collonies of cells would employ?

    • In reply to #3 by Nitya:

      That was a great article and I appreciated the photos. I wonder what response WLC would have to offer if he were to look down the microscope. No doubt he would find some flaw in the procedure.

      Isn’t his usual scientific problem an inability to focus?

  2. My particular interest in this problem is thwarting HIV viruses from developing resistance to anti-retroviral drugs.

    If you could predict the evolution, you might not bother with a drug that will have a short life, or tinker with it to make it harder to beat before you even release it, or tinker with it shortly after you release it.

    I got to have a look at the DNA profile of my HIV which have evolved mutations allowing it to defeat nearly every drug in the pharmacopoeia. What surprised me is only one mutation is needed to defeat each drug. You might think it would be possible to predict that mutation and do something about it ahead of time, perhaps a drug that specifically targeted HIV with that mutation.

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