How to Preserve Microorganisms: Store Your Cells Better

Learn the fundamental reasons for preserving microorganisms: maintaining dormancy, preventing contamination, and avoiding genetic changes. Understand that low temperatures and freeze-drying techniques reduce metabolic activity without harming cells.

Store microorganism agar plate cultures in a laboratory refrigerator at 4°C on growth medium mixed with agar. Wrap plates securely with laboratory film and store upside down to prevent condensation and contamination.

Pick a single colony with a needle and stab it into soft agar and growth media in a sterile tube. Cap the tubes and store at low temperature; stab cultures typically last from two weeks to one year depending on species.

Resuspend cells in growth media containing cryoprotectants such as 30% glycerol or skimmed milk before freezing. Freeze stationary-phase cultures at -20°C, -80°C, or in liquid nitrogen for optimal cell viability.

Store frozen cultures at -20°C for at least one year or at -80°C or in liquid nitrogen for decades. Retrieve cells by gently thawing at 37°C and inoculating into fresh growth medium.

Use lyophilization to remove moisture from frozen samples through sublimation in a vacuum, creating dry cell pellets. Recover freeze-dried cultures by rehydrating pellets in appropriate growth media before inoculation.

Entrap microorganisms in protective encapsulating materials such as gelatin, ethyl cellulose, polyvinyl alcohol, or calcium alginate before storage. Microencapsulation shields cells from harsh freezing and drying stresses while improving viability during storage.