What is a common method for preserving microbial cultures?

Freezing or lyophilization (freeze-drying) is a widely accepted and effective method for preserving microbial cultures. This technique helps maintain the viability and physiological characteristics of microorganisms over extended periods.

When microbial cultures are frozen, the low temperatures inhibit metabolic activity and prevent cellular processes that could lead to degradation or death. Moreover, freeze-drying involves freezing the culture followed by the removal of water under vacuum, which stabilizes the organisms and allows long-term storage. This method is particularly advantageous because it reduces the risk of damage that can occur from ice crystal formation during freezing.

In contrast, culturing in agar plates is primarily a method for growing microorganisms rather than preserving them long-term. Storing cultures at room temperature may lead to rapid degradation or contamination, thereby shortening their viability. Using chemical preservatives can alter the metabolic state of the organisms and may not effectively guarantee long-term preservation without influencing the cultures' characteristics. Therefore, freezing or lyophilization stands out as the ideal choice for effectively preserving microbial cultures.