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regular_modern_girl t1_it4axd4 wrote

Reply to comment by Upset-Ad4844 in Why does alcohol kill bacteria, but not the cells that our bodies are composed of? by Chairman_Mittens

Yeah this is part of why I added the “chemicals they’re not specifically adapted to” bit, because to my knowledge you can name practically any harmful chemical and there will be at least one bacterial species that is extremely tolerant of it, if not completely unaffected. There are bacteria that can survive in heavy metal-laden mine runoff so contaminated that it looks like blood and has the pH of white vinegar, there are bacteria which live in steaming sulfuric acid-filled volcanic caldera lakes, there are halobacteria that thrive in bodies of water over ten times the salinity of the ocean, and there are even bacteria that can survive being irradiated (apparently in part by having lots of redundancies in their DNA and being really good at repairing DNA with minimal errors).

And that’s just actual bacteria, because there are also archaea (not actually bacteria, but historically conflated with them) that can survive in such extremely high temperatures that their specially heat-adapted enzymes are actually an indispensable tool in biotech (in particular, PCR makes use of a thermophilic archaeal DNA transcriptase so that it can speed things up with higher temperatures, iirc). Obviously this is different from chemical resistance, but it just goes to show how there are microbes that can survive almost anything.

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Upset-Ad4844 t1_it4djaf wrote

Thanks for your very complete and excellent response

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molbionerd t1_it4k02r wrote

great explanation! its crazy the environments that bacteria can survive. Waters bears too.

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regular_modern_girl t1_it54440 wrote

this is admittedly really pedantic (although this might actually be more of a popular misconception than I’m thinking), but technically water bears can actually survive (at least in terms of like, actually actively living in) only in a fairly narrow range of conditions, requiring freshwater aquatic habitats in a fairly moderate temperature range (they can live in extremely thin films or tiny droplets of water in otherwise terrestrial environments, but that’s about the most extreme they get when actually living, breathing, eating, and mating), it’s more that they can enter a state of cryptobiosis (called a “tun”) which is incredibly resilient to extremes, up to and including the conditions of outer space or near-absolute zero temperatures (and then having their frozen tun state used in a quantum double-slit experiment, and still being successfully revived after lol).

So with water bears it’s more that they’re really good at weathering extremes, but not necessarily actually living in them per se, whereas bacteria and archaea can often actually exhibit active cellular metabolism and other processes even in some really extreme habitats.

I mostly just mention this because I’ve seen a lot of people say that water bears are “extremophiles”, when really they’re actually somewhat on the fragile side while actively alive, they just have a very resilient hibernation-like state they can enter, basically.

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molbionerd t1_it56pbc wrote

Yes they are not actively growing in those environments, but as long as they can return to that active state, they are alive. Many organisms (especially “simple” organisms like bacteria and lower eukaryotic life) are able to enter these non-metabolically active states, sometimes with extra protection (like the water bears, spore forming bacteria, and lots of fungi and yeast) allowing them to survive those extreme conditions. Arguably this is ability is more interesting and without a doubt it’s more important for the survival and dissemination of life across earth, and potentially across the universe. We may have already spread them ourselves :)

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TrogdorLLC t1_it5k5uk wrote

They are already on the Moon, thanks to an Israeli lunar probe that crashed there.

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Quantum-Carrot t1_it6md6p wrote

I watched that stream live. That thing must have hit the moon at like 500 km/h. Maybe some of the ejecta will land on another planet?

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Misterbellyboy t1_it7wamp wrote

Isn’t that why permafrost melting in places like Siberia could be kind of alarming? A bunch of hibernating prehistoric bacteria that we’ve never had to deal with before “waking up” again or something like that?

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ptmmac t1_it72nhr wrote

Bacteria are amazingly adaptive, but nothing shows the absolute persistence of life like the radiotrophic fungus found in the reactor at Chernobyl. This fungus actually uses melanin to produce energy for the organism. It isn’t just surviving radiation, it is feeding off of it.

The original poster does not seem to understand how ephemeral the boundary between organisms and their biome is in practice. The colony of bacteria is equally unaffected as the macro organism is to the death of individual cells destroyed by alcohol. If you don’t brush and floss, but do use mouthwash you will have major problems with gum disease. Less then someone who does nothing but still severe enough to reduce your life expectancy.

More to the point if you did kill all the bacteria in your body you would die from malnutrition if nothing else.

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