Sodium chloride, or salt, has endless uses in our everyday life. Salt helps our bodies function properly. Additionally, salt's ability to prohibit the growth of bacteria makes it a valuable preservative.
The common salt molecule is made up of the elements sodium (Na) and chlorine (Cl). The negative chlorine atom attracts the positive sodium atom to form an ionic bond. Water readily breaks the ionic bonds, leaving positively and negatively charged atoms in the solution. This can form a gradient for other charges to move to or away from.
Bacterial cells contain a structure known as the cell wall. The wall is semi-permeable, allowing only water and very small molecules to pass through. Usually, bacteria grow in an aqueous solution in which the concentration of the water on the outside of the cell wall is higher than inside of the cell. This results in the flow of water into the cell.
Effects of Salt
If salt is added to the aqueous solution surrounding bacterial cells, the concentration gradient is essentially reversed. This causes water to flow out of the cell. According to Ask the Scientist, if the concentration of salt outside of the cell remains elevated, the bacterial cell will become dehydrated and die.
Although salt will harm most bacteria, a few species have adapted the ability to survive in a salty environment. Members of the Staphylococcus genus tolerate salt. These bacteria are common to the skin, which is salty due to sweat.
The preservation of food has been accomplished by salt for hundreds of years. Treating meat and other foods with salt will keep it edible for longer. Salt prohibits the growth of harmful pathogens by removing the water source. Additionally, salt produces an electrolyte imbalance in the cell. These factors contribute to preserving the food for longer periods of time.