> The experiments, described in the Sept. 9 issue of Science, are thought to provide the first large-scale glimpse of the maneuvers of bacteria as they encounter increasingly higher doses of antibiotics and adapt to survive — and thrive — in them.
The BBC TV programme Horizon showed the same giant petri dish 4 years ago. This post contains a link to a slightly different clip with a smidgen more background.
The other scary bit is that the 100x is toxic to humans, and that they cannot add any more drug to the 1000x because they've reached the limits of solubility.
Haven't read the paper yet. But I expect to see a control where they plate the same starter culture directly on each log scale antibiotic concentration (1,10,100,1000) to see if it contained resistant bacteria from the get go. Thus testing if resistant mutants were always present in a population or they arise and are selected for by evolutionary process.
It is the origin of mutants that is the more interesting question.
I am curious - Are the bacteria really "evolving" at each subsequent boundary? In the article/video, they specifically mention "mutations". That says to me, that the bacteria are literally experiencing mutations within their nucleotide pairs, that results in them becoming more resistant to the drug?
Couldn't it also be that among the initial population, there existed 1 (or more) very very strong bacteria? At each boundary, the weak ones are dying off (hence the pause in growth) while the strong ones continue to reproduce. Since they're strong, but few, you witness a lag in overall growth of the population which the article is saying is the "evolving" process, when really it's more of a filter process. Filtering the strong, from the weak, by progressively stronger antibiotic strands.
I guess ultimately I'm just wondering what they specifically mean by "evolve" and "mutation".
Even if the mutation was part of the original soup of bacteria, the process in the video still shows evolution. Either at time=0 or some point in the future, a strain of bacteria was more fit to survive and produce viable offspring than the others that died off in the presence of the antibiotic doses.
I'd guess not. In many cases, these sorts of mutations are maladaptive outside of that environment.
Put a polar bear in the tropics and it's not going to do so well - not just because it's going to overheat, but because all the energy spent growing that hair could've been better used on something else.
This concept is key. Growth in the presence of antibiotic in pure culture on agarose plates does not necessarily equal pathogenic potential. Every adaptation probably has a cost to the bacteria, and if you throw in the immune system and other competitive bacteria that may not be pathogenic, those 'super bacteria' may be less super. All that said, as a microbiologist, antibiotic resistance terrifies me, with the current economics of new drug development being as daunting as the technical challenges.
I would love to see this done with various bacteria against other chemicals. For example, Bleach. Bleach denatures cells so in theory it would never happen but it would be an interesting experiment.
I'm not sure bleach would be that interesting. It's like asking deer to evolve resistance to hunters' rifle bullets--it's too steep an evolutionary step.
Is it though? Imagine a world in which the only agent of selection was hunters bullets. No sexual selection, no food shortage, nothing. In other words, an absolutely perfect deer breeding ground.
Place a billion deer in this environment and shoot them all. A few survive. Let numbers rise, and do it again.
Soon you start seeing deer with arteries and veins that are smaller, blood that clots faster. Maybe the deer themselves are smaller, or their internal organs are smaller but their muscles larger, fed by a larger number of smaller veins. Perhaps muscle density is higher to offer better protection. Bone and skull thickness increases.
Eventually you've got an animal with a small, very thick skull, with lots of angles to increase the likelihood of ricochet, a heart protected by layers of thick muscle and a reinforced, thickened ribcage. Veins and arteries are reduced in size so much that it's practically impossible to bleed out, immune system is in constant overdrive to fight infection, and the rest of the internal organs are either shrunken, duplicated, or hardened against piercing damage.
In any case, my point is, if we could set up an experiment with deer like we can with bacteria, I think it's likely that we'd be surprised at what's possible.
Well done on the deer analogy- I'm in over my head there. I appreciate and agree with your point, and think my original response was glib and not clear. Clearly, extremophilic archea have evolved to inhabit nearly every niche of the earth (Deinococcus radiodurans is a great example). The point I took from the video was not that bacteria are rapidly able to adapt to antibiotics, that’s been known as long as antibiotics have existed, but the observation of the instant in time when a bug figures out one of those discrete changes and its offspring thrive.
I believe the scale and breadth of adaptations required to observe evolution of meaningful resistance to a universal denaturant such as bleach would be prohibitive. Bleach destroys at the level of protein chemistry, where as antibiotics are specifically toxic to bacterial structures. The wholesale changes would be required of the organism, rather than discrete mutations in the ribosome, cell wall, or other mechanisms known to drive antibiotics resistance-probably what you can see changing in the video. My awkward comment was intended to say I don’t think the scale and time frame of the video assay would not be amenable to the scale of the study for bleach resistance. You illustrate that same point in your comment. That said this is all knowable first-hand, as generating or isolating bacterial strains resistant to toxins is science one could do at home with probably less investment that homebrewing beer, although without the fancy movies.
Taking this discussion a step further: in the bullets/deer instance, you'd be more likely to evolve a primary lifeform that looked more like a tree or grass or slime-mold than a deer. That is, it either consists almost entirely of bullet-stopping material (wood), or is so lightweight that bullets don't effectively transfer energy to it (grass), or the structure is entirely decentralised such that a bullet, or even a hail of bullets, cannot disrubt the systemic function of the organism -- it simply absorbs the projectiles and functions around them.
A chlorine adaptation, if possible, would be along similar but chemical lines -- you'd end up with a non-protein based chemistry, or something not affected by chlorine, or which could buffer it to extreme levels.
Differential resistance to bleach at low concentrations might be possible to breed for. That could be interesting. In a similarly horrifying sort of way.
I agree, but also think one has to consider the mode of action of the poison and the evolution of mechanisms of resistance to it. All poisons are not equal. Sure, generating some level of bleach tolerance is possible--studies using it as a model for oxidative stress have been published in the scientific literature, but i really think that 'meaningful resistance' as observed in the videos would take a long time.
This brings to mind how quantity will always beat one super power.
Example one bee will not kill a large predator but a swarm will.
One termite is joke but thousands will bring down a house.
I suspect one antibiotic will never beat bacteria in the long run.
Looks to me like it's a never ending battle. I hear about the post antibiotic era like we had won the war at one time. What we won was a battle in a never ending war.
We hear about technology fixing all and jobs ending. Here's an area where there will always be a need for research and solutions.
This reflects the importance of the dosage and duration when taking antibiotics.
This video shows hormesis[1] at its best: How bacteria is able to develop resistance over an increasing dose of antibiotic. I doubt that they would have been able to survive when exposed from 0 to x1000.
Bacteria have a solution to that too though with the use of mobile genetic elements called plasmids. So the genetics of something can float in the population with locality to its relevance. Most antibiotic resistant bacteria in hospitals get their resistance from ground dwelling bacteria people walk in with their shoes.
The BBC TV programme Horizon showed the same giant petri dish 4 years ago. This post contains a link to a slightly different clip with a smidgen more background.
https://news.ycombinator.com/item?id=5356309#5356479
The other scary bit is that the 100x is toxic to humans, and that they cannot add any more drug to the 1000x because they've reached the limits of solubility.