Biology: We all know about bacteria immune to anti-biotics. Couldn't some also evolve immunity to other means of killing them, like alcohol, heat, soap, air (...add others you can think of)?

Catten · 1 year

Yes, but there are physical limits to how much a biological system can handle and how much they can adapt before the drawbacks to the adaption (e.g. energy cost) outweighs the advantage.

That is not to say that it does not happen. Soap does not kill all bacteria for instance, the strains with a thick cell wall can take a surprising amount of abuse.

Of course this does not help us much, since out cells are more sensitive to this kind of treatment than the bacteria...

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chrisamiller · 1 year

Most antibiotic resistance works by circumventing the targeted protein in a biochemical pathway. The redundant nature of these pathways makes this fairly easy to accomplish with only minor mutations to just one or a few proteins.

Alcohol denatures proteins, making them lose their structure and function, and lyses (think explodes) bacterial cells. This can't be defended against in any simple way. It's like asking why humans don't evolve a thick armor plate to defend against gunshots. It would require serious modifications and represents a huge evolutionary hurdle.

That's not to say that all microorganisms are completely vulnerable to alcohol. Some critters that have a spore stage are well-defended from things like alcohol and extreme temperatures. Don't worry too much about that, though. In general, alcohol is, and will continue to be, a great disinfectant.

Platypuskeeper · 1 year

Well they can evolve tolerance of these things. Enough heat or enough of almost anything will inevitably kill an organism, no matter how hardy.

That said, there are plenty of organisms which are quite reistant to various things. Pyrococcus furiosus is a bacteria that thrives at boiling temperatures. But that's nothing compared to Deinococcus radiodurans, an extremely tough bugger who's highly resistant to radiation, acid, dehydration, even vacuum.

But there's a difference here; these bacteria have evolved over millennia. Antibiotics resistance is acquired relatively fast, because antibiotics need to be harmless to human cells and preferably specific to certain bacteria as well; you don't really want to eradicate all the bacteria in your body. This usually means that there's a relatively minute difference in the biochemical pathways that allows humans and some bacteria to survive, and not others. Since the difference is small, it can evolve resistance faster. Sometimes all it takes is a handful of mutations.

So yes, bacteria can and have evolved tolerances of these other things. But it takes a lot longer to do so.

kraffft · 1 year

I think the trick is that the things germs/bacteria have difficulty adapting to, humans do as well, so those things aren't useful as antibiotics.

bdunderscore · 1 year

Sure, but they might also end up at the same time evolving to be unable to survive within the human body. The problem with antibiotics is they're intended to eliminate bacteria without harming the human body, so they are both easier to adapt to (after all, our cells are immune...) and there's simultaneous selection pressure to stay adapted to the human body. Things like alcohol, heat, soap, air, bleach, etc, are toxic to almost everything, including us, and adaptations to them are costly and can make it difficult to survive in milder environments - and since they aren't applied in the human body, there's no simultaneous selection pressure to remain adapted to the human body.

faswich · 1 year

Extremophiles, one of the topics that hooked me on biology.

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