There are several ways in which salt and sugar inhibit microbial growth. The most notable is simple osmosis, or dehydration. Salt or sugar, whether in solid or aqueous form, attempts to reach equilibrium with the salt or sugar content of the food product with which it is in contact.
It's a disrupter that wreaks havoc in microbes, interrupting their enzymes and chipping away at their DNA. It most often works through dehydration, removing many of the water molecules that bacteria need to live and grow
