Why do I see only high temperature advice to kill microorganism, and not low temperature?
Why isn't there any low temperature which kills virus? Are they more resistant to low temperature?
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1$\begingroup$ To re-create the spanish flu of 1918, they tried to collect it from graves from very cold countries like siberia, because cold temperatures stop most micro-organisms like pause on a TV, and when they wake up, they just keep going. $\endgroup$– bandybabboonCommented Mar 17, 2020 at 19:35
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1 Answer
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High temperatures means that lots of energy is available in the environment. This energy speeds up chemical reactions, and make possible some reactions that wouldn't happen at all at lower temperatures. In particular, proteins can adopt new shapes as temperatures get higher. It's the misshapen proteins rather than the temperature per se that kills the microorganisms.
Low temperatures mean there is relatively less energy available in the environment. This slows down or stops chemical reactions, including the ones that result in mis-shaped proteins. Extremely low temperatures may slow down a microorganism's metabolism and stop it from reproducing. That's why we keep perishable foods in refrigerators. However, if you warm the microorganisms back to a normal temperature, most of them will pick right where they left off. A few may be killed by the formation of ice crystals inside the cells that mechanically break the cell membrane.
If you walk into a microbiology lab you'll often see a wall of refrigerators, used to preserve microorganisms for later revival and use.
answered Mar 17, 2020 at 18:18