Given that bacteria are hypertonic (contain more salts) compared to distilled water, and that they rely on ion concentration differences across the plasma membrane to survive, can I kill a bacterial solution by adding an excessive amount of distilled water to make them explode? If I add distilled water on a surface, are the bacteria on it going to die?

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    $\begingroup$ Counter question: If you think this is so easy, why are surface disinfectants used instead of water? $\endgroup$ – Chris Feb 5 '18 at 21:49
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    $\begingroup$ maybe because disinfectants have a wider spectrum of species that they can kill? maybe distilled water would kill some species but not all? I don't know. I would like an explanation of why then distilled water is not used as a disinfectant. $\endgroup$ – charlesdarwin Feb 5 '18 at 22:13
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    $\begingroup$ In addition to @Superbest's answer, distilled water does not remain 'distilled water' from the moment it touches a washcloth, sponge, surface, etc. You would need to literally flood your counters with the stuff to do any disinfecting, and at that rate, probably anything you use (e.g. tap water) might be just as effective. $\endgroup$ – anongoodnurse Feb 6 '18 at 7:33
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    $\begingroup$ @Chris: this is the kind of answer/comment which shuts down interest and research. "Because" comes just below in the rank. And then "Don't ask stupid questions". $\endgroup$ – WoJ Feb 7 '18 at 18:25
  • $\begingroup$ @WoJ: There are four types of answers, and counter-question is one of them. $\endgroup$ – user37894 Feb 8 '18 at 9:24

Indeed, bacteria are susceptible to osmotic stress from being in pure water. They are also susceptible to starvation in such an environment.

However, wild bacteria tend to have many mechanisms that protect against this and allow them to survive in spite of being exposed to water. Note, also, that freshwater can serve as a habitat for many species of bacteria: Consider ponds, streams, lakes, etc.

Thus bacteria which you encounter in everyday life will likely have been those that survived osmotic stress in the first place. And drying, and mild disinfectants, and sunlight, and temperature variation... So it is unlikely that water alone will kill them.

Here is a recent article on this topic: http://jgp.rupress.org/content/early/2015/04/07/jgp.201411296.short

And here's one about how osmotic stress affects susceptibility to other antibacterial effects: https://www.sciencedirect.com/science/article/pii/S0740002014001890


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