Why is cooking still an effective way of eliminating human pathogens or fermentation or salting? These methods do not eliminate all traces of the bacteria so what is keeping a random mutation from happening that allows, say, e. Coli in beef to become resistant to heat up to 60c or Listeria to resist salt concentrations to the same levels as bacteria which are not infectious and potential beneficial to us that can tolerate?
What is it about antibiotics that makes them so susceptible to creating these random mutations that antibiotics become near obsolete in decades?
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Heat and salt both directly affect the core functions of life, meaning it is extremely difficult for a single form of life to evolve to handle wide ranges, and those difficulties are amplified for smaller life forms (eg bacteria) than for larger ones (eg mammals).
Notably, heat affects water state, protein structure, and the speed of chemical reactions. This means the basic chemistry of life needs to be different at different temperature ranges, and those that work well at higher temperatures are much less suitable for lower temperatures. There are bacteria and fungus that live in hot springs, called [Thermophilic Bacteria](https://www.nps.gov/yell/learn/nature/thermophilic-bacteria.htm), and are one of the main factors giving Yellowstone hot springs their characteristic colors, however they cannot survive at the more “normal” temperatures that we live at.
Salt has similar major effects in the behavior of chemistry, and most life can only survive with fresh water or salt water. All life needs some amount of salt for proper functionality, and thus it cannot be completely blocked out. A handful of larger organisms can manage to switch between the two, but not many – they are called [euryhaline species](https://en.wikipedia.org/wiki/Euryhaline). There is actually life that lives in [briny water](https://en.wikipedia.org/wiki/Brine_pool#Microbial_diversity_and_community_composition), which is much saltier than sea water, but it will die in fresh water. The wider the spread of salinities, the harder it is for a single life form.
Antibiotics, on the other hand, interfere with specific functions of the bacteria and are not core to the basis of life. As such, it is easier for mutations to block uptake of a specific antibiotic as the core functions of their life do not rely on the uptake of that specific chemical. Such evolution is typically based on slightly changing the shape of specific receptors on the outside of the cell or slight tweaks to the proteins that transfer chemicals into the cell.
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