Mega-Plate Petri-Dish Lets You Watch The Evolution Of Bacteria

Rearchers of the Harvard Medical School built a 2 feet by 4 feet (61 x 122 cm) large petri-dish to visualize the evolution of bacteria. Their experiment induces mutations in E. coli bacteria by exposing them to gradually increasing concentrations of antibiotics.

Their assembly consists of a large glass tank with a thick agar at its bottom and a thinner agar on top of it, which acts as a mobility layer, allowing the bacteria to move around in the dish. The bottom layer is divided into 9 bands, which are treated with gradually increasing concentrations of antibiotics: No antibiotics in the outer bands, one time the lethal concentration for the bacteria in the second most outer bands, with each band increasing the concentration tenfold until it reaches 1000 times the lethal dose in the center band.

Then the E. coli bacteria enter the playing field. Every time they reach the frontier to a new band, they are forced to develop new mutations to survive in the harsher environment. When they finally reach the center band after 11 days, they are able to withstand a thousand times more antibiotics than their wild type could survive. The way the researchers set it up, their experiment lets you watch the evolutional pedigree of each mutation branch in a flat-out astonishing way. Enjoy the science below!

49 thoughts on “Mega-Plate Petri-Dish Lets You Watch The Evolution Of Bacteria

    1. The fear of super bugs is distorted by misinformation, it is not true to say that we have only discovered 3 or 4 new antibiotics in decades, the truth is that the biotech companies can’t be bothered going to human trials with the ones that they have found because there is currently no financial incentive to do so. There are also far more effective genetic systems on the horizon that should be a game changer. They work because bacteria are total sluts when it comes to DNA sharing so if you combine toxic DNA with antibiotics only the less promiscuous bacteria survive but they can no longer pick up or pass on resistance genes so easily because they had to turn that function off in order to survive the toxic DNA. Even cycling 3 different antibiotics the right way will break their adaptation mechanisms.

      1. Up until recently there was a lapse in new classes of antibiotics, so it is a bit of a worry.

        Saying you’ve discovered a new antibiotic is like saying you’ve discovered a replacement for hydrocodone when really all you’ve done is slapped an extra couple functional groups on it to side step a patent and maybe decrease side effects. Except with antibiotics discovering a new antibiotic only matters if attacks a new pathway (specifically non beta-lactam for stuff like MRSA).
        Throw in over-prescription, failed dose completion, and lethal side effects, and you can see why big-pharma is slow to roll out truly new drugs. Why bring out the big guns that you’ve just started developing if you can’t ensure they won’t just make the problem worse by the first 2 issues I pointed out.

      2. Not sure about the fear of superbugs being founded on misinformation — there’s plenty of evidence from hospitals that they’re present and that they’re hurting people. I think that it’s the hospital environment, with a low level of _every_ possible antibiotic, that does it. Strictly cycling, in strong enough doses, should work like you suggest.

        On the other hand, this experiment is quite safe. I’ve done it myself as a freshman. You evolve them to be super-resistant to penicilin, and then one you’ve been graded, you clobber them with kanamycin or similar. Lights out, “super”bacteria.

        This demo, in a big-arse petri-dish, is awesome.

        1. The fear is founded on misinformation, the fear. Ask most people and they will tell you something to the effect that we have run out of options, but the truth is we stopped testing all the options that are on the books. i.e. The average person’s perceptions of the situation are not exactly founded on fact. See what I mean now?

          1. One way or another, they don’t exist. One way or another, we’ve, collectively, rendered the existing arsenal increasingly obsolete.

            You are spreading your own strain of mis/disinformation,

        2. I consider it an amusing coincidence that superbugs became the FUD of the day real soon after people started tearing into drug companies for taking public and charitable research funding, patenting the results and charging out the arse for it.

        3. I’ve been in medicine for over 25 years now. We talked about antibiotic resistance being a serious issue the very first year I started, academically, and I saw a couple of physicians taking a stand on it professionally, but they definitely stood out.
          I’ve worked in hospitals ranging from dirt floors to state-of-the-art cutting edge facilities. My last six years I noticed a very serious trend (I state six, because I saw it in Haiti, already in place when I got there): hospital-wide coordinated use of antibiotics. Not necessarily used for routine outpatients, but in many cases, admitted patients antibiotics were examined and approved by an infectious disease specialist, and in every case and ID specialist could switch an antibiotic with very little resistance from the primary doc.
          To the folks that say that antibiotic resistance isn’t a thing, walk through any trauma ICU, or probably any ICU at this point. Talk to a hospital clinical case manager.
          Go look at the TV, and look at the ads for lawsuits against pharmaceutical companies. Lawyers are getting rich suing because of known side effects (A drug that prevents your blood from clotting could make you bleed more… who’da thunk it?). That’s the equivalent of suing auto makers because your car makes you walk less, or burns your leg when the seat belt buckle gets you during the summer. Pharma is nervous about developing new drugs? You bet! It’s an incredibly adversarial process, can take a decade, and once you get there, the lawyers are literally reading your drug information to see how they can sue you (and succeed, over and over again).
          I’m not excusing Shkreli or Mylan for their obscene price gouging. That’s utterly inhumane (Hey, hackers, build an epi-pen. The drug itself is literally pennies a dose). But we’re talking about two extremes here.
          In the middle are an insane number of people, incredibly devoted to the cause of healthcare. The vast majority of which don’t make more money (I make a TON more since I put medicine on the back-burner). The goal is to help people in pain, something that they take very seriously, and drives them forward.

    2. I have been a doctor for 36 years. My pre-med college professors were talking about the fearful spectre of multidrug resistance in the early 70’s. I have never heard of even one local patient succumbing because of an infection caused by a superbug with no resistance to anything. I am NOT saying that people do not die of infection. Elderly, sick and immunocompromised people die of infection all the time. I am not saying that we should ignore attempts to produce new antibiotics or that drug resistance is not a problem. I am saying that it is a workable and predictable problem.

      The media love superbugs. What happened to the flesh eating bacteria epidemic 5 years ago? The media has moved on to other P. T. Barnum pusuits.

      How many times over the years have you heard about a new infection of honeybees that is going to wipe out our food supply? About every 2 years. Same thing. Bad science, no. Honeybee diseases do exist. Bad journalism, yes.

      1. AIUI there’s bacteria out there that are immune to everything except one antibiotic, usually kept as a last resort. Maybe it’s a strain of MRSA. Drug resistant bacteria are becoming more common. Which is pretty obvious really, not completing a course of antibiotics is basically evolving stronger bacteria.

        The bee thing is true, bee populations are plummeting, and nobody really knows why. That’s a sign, a drastic fall in population is a prelude to extinction.

        Of course the media bullshit, all the time. “News” is pretty much worthless. There’s a germ of truth, but the meaning and interpretation is complete hyperbolic nonsense, that doesn’t resemble the actual truth. But it doesn’t mean there’s never any problems.

      2. This isn’t yet a technical problem, but it is a financial one. When the antibiotics we are all using now were discovered and developed they had a good chance of decent market price and wide use. A new class of antibiotic released now, capable of treating resistant bacteria would be too precious for general use, it would kept as a last resort antibiotic and have a high probability that even if medically successful would fail to earn back the investment.

        It’s looking increasingly likely that governments are going to have to step in and legislate or contribute financially. Public approval for that and the media coverage that can help generate it are all part of the process.

  1. That is a brilliant and illustrative experiment, but it is no surprise that bacteria can adapt to antibiotics as they evolved them as defences against other bacteria in the first place and they have been doing it for at least 3 billion years.

    What I’d like to see is two types that have different colours, natural or engineered, that compete against each other, or a fungi vs bacteria battle. Perhaps even a bacteria vs phage version? Not that you could see the phage as it is a virus, but it could be engineered to make the bacteria change colour before it died.

    1. I was totally confused and couldn’t understand a word of the article because of that extra apostrophe. I’m glad you are calling HAD to task for ruining my day.

      BTW, where I grew up, the final period is supposed to be enclosed inside the quotes, not after the closing quote. It took me fifteen minutes to decipher what you wrote because of your careless punctuation. I don’t know if my brain can withstand this continued assault on proper grammar and punctuation.

      1. Then you probably grew up in the USA. You are forgiven for being unable to use English properly.

        I don’t care what people write in the comments. Seeing that someone is unable to string a sentence together helps when deciding whom to listen to. However, headlines and articles should be held to a higher standard.

        1. My point wasn’t that the period *should* be inside the quotes; I recognize there isn’t a universal convention. I was making fun of the fact that a minor error was so off-putting to you. I come to hack a day for the content and links, not the grammar. This is a glorified collective blog, not a publishing house.

    2. Does it matter? Is the information good enough to get the gist? Does it detract from the overall content any more than any distortion you receive in every day life? English is a stupid language with a bunch of stupid rules that do not always add to a clear understanding. Only the minority really care, and most people don’t relate to your boring snovel. Don’t like it join the hackaday team when they ask for jobs.

        1. English is an evolving language, and should be treated as such. And comparatively , knowing 3 different languages, english isn’t always best for clear communication(a good example would be for “love”).Clearly written English is fine, but it doesn’t always aid for understanding. I just don’t get how someone could think about something for 15 minutes because of a apostrophe catastrophe. That blows my mind.

          1. there is no more lazy cop out in language and grammar than the “language is always evolving” platitude.
            i agree that in the case of a single apostrophe most should have better to do, but then someone on the internet says something stupid…..

            like how language always is evolving and that that in some way means we shouldn’t care about the language that we are actually using at this moment, language evolves, yes, but the way it does so requires a large amount of consistent change, not a random guy misspelling something on the internet a couple of times, so until we see people consistently not use apostrophes over a large enough fraction of the worlds English speakers, then and only then would it begin to evolve.

        1. Best I could find was microbes that produce biofilms are resistant to low concentrations or short exposure times.
          Just like antibiotics, following the directions kills every thing.
          I could believe hospitals stepping away from bleach & other hypochlorites for environmental concerns but not due to efficacy.

  2. “gradually increasing concentrations of antibiotics”

    Huh? Did no one else’s mental siren and flashing red lights go on? It’s for exactly that reason that you MUST finish a course of antibiotics prescribed by your doctor, so that so no antibiotic-resistant E-Coli or any other bacteria are left to escape and infect other people (as is already happening in Africa, and in hospitals around the world).

    Exposing the bacteria to gradually increasing concentrations of antibiotics is a great way to make antibiotics ineffective, and is a crime against humanity.

        1. They absolutely should, it’s thought to be partly responsible for resistant bugs.

          As for the experiment, can these bacteria colonise humans? While the strain is harmless, isn’t there a risk of them sharing plasmids with something worse, and creating an actual danger?

    1. Many mechanisms of drug resistance involve the use of protein efflux pumps which shuttle antibiotic out before it can negatively affect biological function. Once the bacteria evolves this once, it is simply a matter of pinning more proteins in the membrane.

      1. It’s interesting stuff. The antibiotic itself is still effective “poison”, but the bacteria has devised a way to pump it out to keep the concentration low enough to be ineffective. Some researchers are now looking at two-part antibiotics: take the original drug, and add something that prevents the bacteria from using its new defense method. So an antibiotic plus an anti-anti-antibiotic : )

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