Principle Microbiology

Low temperature : -
The low temperature method is not used as the method of sterilization as it does not assure sterilization. Temperature below optimum depress the rate of metabolism and if the temperature is sufficiently low the growth and metabolism cease.
Low temperature can be used for preservation of culture.
Agar-slant culture of bacteria, yeasts and molds are stored for long period of time at 4 to 7 degree C.
Many bacteria and viruses are stored in deep-freeze unit at temperature of -20 to -70 degree C.
Many viruses and microorganisms, and stock of mammalian tissues are stored at -196 degree C in liquid nitrogen.