when a disinfecting agent says it kills germs, by what method is it doing so? Does it dissolve the bacteria? Poison them?
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something related to chemically dissolving their proteins and outer layers, from which they essentially “bleed out” their innards and die.
soap to make the surface slippery so the majority wash away
disinfectant to kill any remaining critters.
Cell walls in bacteria are made of proteins, most disinfectants like alcohol or hydrogen peroxide dissolve these walls, letting the insides out.
One of three general ways.
Way 1 is poison – antibiotics are poisons. However, medical planners are trying to move away from these where possible because germs can become immune to them, which means they stop working.
Way 2 is effectively burning. Hydrogen peroxide is the most notable case of this; though there are some others. Oxygen (and some other atoms) loves connecting with whatever other atoms are handy – and while in water the two hydrogens keep the one oxygen busy, in hydrogen peroxide, there’s one oxygen too many and it wants to grab something – and it’s quite happy to grab something that keeps cells alive as anything else. This is also why peroxide stings – your body is reacting to being hurt.
Way 3 is taking the skin off. All cells, including bacteria, have a “skin” made of proteins and lipids (fats). Soap and alcohol based cleaners disrupt this skin, allowing their insides to leak out – it would be like a human bleeding out, but also having your organs leak out.
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Separately, washing your hands also means that the surface that bacteria are holding on to isn’t on you any more; because the dirt and outer layer of (dead) skin cells get washed away.
It depends on the disinfection agent.
Most chemical disenfectants react with and break down the chemistry of the cell well, usually through the process of oxidization. Its ok to think of this as dissolving them into their base chemicals. These are your chlorine chemicals like bleach, ozone, and your peroxides.
Alcohols and soaps bond with the proteins in the cell membranes and cytoplasms, weakening them. Kind of like poking a hole in the container, which makes them effective at killing simple cellular organisms like viruses and bacteria. Go for 70% over the 98% isopropyl as it has more water which gives it a greater reaction time and kill rate.
Pressure and temperature damage cells and essentially burn/boil microorganisms.
UV disenfection irradiates and damages the cellular DNA which prevents them from reproducing and functioning.
Certain agents are more effective than others depending on material you are trying to disinfect and it’s quantity.
All require specific amounts of time to work effectively.
Chemically, Oxidizers tend to work fastest, but can react with and damage the materials you are trying to disenfect and/or cause other harmful chemicals to be formed. Also, cyst and spore forming microorganisms are partially resistant.
Alcohols and soaps are less effective than oxidizers, but good enough, cheap, and ideal for everyday small scale use in the home.
Temperature and pressure are both also fairly quick and work best on things like equipment, dishes, etc. But it is energy and resources intensive and require machines like dishwashers, autoclaves, etc. They are extremely effective and killing all but the rarest of microorganisms if used properly.
UV is highly effective, but requires specialized equipment, a fair amount of contact time, and can be resisted by certain microorganisms.
Here’s a nice video from TED ED:
It talks about the difference between soap and hand sanitizer for covid. This is for viruses, but it is good info about killing microorganisms.
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