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Sunday, February 13, 2011

Bacteria and Soap


In the ‘Soap & Water’ post I talked about how soap behaves to clean away grease and dirt. But I consider that the best part of the story of soap is how it also attacks bacteria.
Bacteria are single celled creatures and there are countless different kinds and astronomical numbers of them living in us and on us forming a part of normal, healthy human physiology. Most do no harm but others can cause infections, diseases like cholera, and diarrhea. We pick up and transfer bacteria with our hands every time we touch something.

Fortunately washing with soap and water can kill bacteria. It does this by distrupting the cell’s membrane that holds it together. The diagram shows a small cross section of the membrane that is just a double layer of lipids. Lipids [or fatty acids] are similar to soap in that they have charged heads and long tails that have no charge so it’s easy to imagine how soap molecules, along with the rubbing you do when you wash your hands, could break down the orderly array and break the cell open, killing the bacteria.
The water in our small town in the Caribbean has bad bacteria in it and I have learned from experience that when I wash fruits and vegetables, if I just put a few drops of dish detergent in the water, enough to create bubbles, that is enough to make things safe to eat raw - it goes without saying that of course you don't rinse. We’ve had no gastro-intestinal problems since we arrived four weeks ago. Soap is antibacterial! Rie

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