What effect does high salt or sugar concentration have on bacteria?

High concentrations of salt or sugar can significantly impact bacteria by reducing water activity in their environment. This creates a hypertonic condition around the bacterial cells, causing water to move out of the cells through osmosis. As a result, the bacteria may become dehydrated, which inhibits their growth and reproduction. By lowering the available water, both salt and sugar can effectively suppress microbial activity, making environments unsuitable for bacteria or mold to thrive. Consequently, the use of high levels of salt or sugar is often employed in food preservation methods to extend shelf life by reducing the potential for spoilage caused by bacterial growth.