Question

When people wash their hands with soap, this limits the spread of bacterial infections. That much, I am pretty convinced of. Duh.

What I don't get is how this doesn't lead to evolutionary pressure on the bacteria to become soap resistant. I'm not talking about anti-bacterial soaps (I understand the FDA no longer recommends these), but just plain old soap and water.

The soap does something (I feel like I've heard a few mechanisms), but the net effect is that it makes the bacteria less likely to spread. How would this not lead to evolutionary pressure that drive bacteria to be less likely to be removed/killed/destroyed/whatever by soap?

Or is it not a problem because soap is just so strong that it's like evolutionary pressure for humans to survive underwater. Sure, if gradually introduced over 1MMM years, we might eventually get gills. But if you just keep drowning people, no one is gonna really evolve gills.

Answer 1

Soap does not lead to evolutionary pressure for bacteria to become resistant because it physically removes bacteria from the hands instead of killing them with chemicals. The hydrophobic tails in soap molecules surround bacteria and lift them off the skin, allowing them to be rinsed away.

Step-by-step explanation:

Soap is an effective tool in limiting the spread of bacterial infections, but it does not lead to evolutionary pressure for bacteria to become resistant. This is because soap works by physically removing bacteria from the hands, rather than killing them with chemicals like antibiotics do. Soap molecules have a hydrophilic head that attracts water and a hydrophobic tail that repels water and attracts oils, dirt, and bacteria. When you wash your hands with soap and water, the hydrophobic tails surround the bacteria and lift them off the skin, allowing them to be rinsed away. Because soap does not target bacterial cells in the same way antibiotics do, it does not create the same selective pressure for resistance to evolve.