Isolation of pure cultures involves separating a single species of microorganism from a mixed population.
Common methods include:
Streak Plate Method:
Procedure: A sterile inoculating loop is used to spread a diluted sample over the surface of an agar plate in a series of streaks.
Purpose: To separate individual cells to form isolated colonies.
Advantage: Simple and effective for isolating bacteria from mixtures.
Pour Plate Method:
Procedure: A diluted microbial sample is mixed with molten agar and poured into a Petri dish. After solidification, colonies develop both on and within the agar.
Purpose: To isolate colonies from a mixed culture.
Advantage: Useful for counting colonies and isolating pure cultures.
Spread Plate Method:
Procedure: A diluted microbial sample is spread evenly across the surface of an agar plate using a sterile spreader.
Purpose: To obtain isolated colonies.
Advantage: Effective for quantifying and isolating microorganisms.
Serial Dilution Isolation Methods:
Procedure: The microbial sample is serially diluted in a series of dilution blanks, and aliquots from each dilution are plated.
Purpose: To reduce the number of organisms and obtain isolated colonies.
Advantage: Reduces the concentration of bacteria to isolate pure cultures.