Chemotaxis (from chemo- + taxis) is the movement of an organism in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment.
It will be good for up to six months, in the vacuum seal, if stored in the refrigerator. If frozen in the vacuum seal, it can last for about 1 year. Once the sample is removed from the vacuum seal, it should not remain at room temperature for more than 18 hours. It will keep in the refrigerator, unsealed, for 30 days.
After opening, it will still be good for six to nine months, as long as it's been continuously refrigerated. And salad dressings sold in the refrigerated section will be good for six months, or until the date on the bottle, as long as they're stored in the fridge at home.