Pure cultures contain only a single type of microorganism and are important for accurate identification, testing, and experimentation. They are obtained through techniques like streak plating that isolate individual cells on nutrient-rich agar plates. Once isolated, various methods are used to prove purity and maintain cultures, like ensuring uniform colony morphology and biochemical reactions. Pure cultures are then preserved long-term through refrigeration, paraffin coating, cryopreservation in liquid nitrogen, or lyophilization to stop metabolic activity and allow viability for years.