Streak Plate Method: Principle, Procedure, Uses  

Written by Acharya Tankeshwar • in General Microbiology 

For organisms that grow well on agar plates, a streak plate is the method of choice for obtaining pure culture. The streak plate technique is used to isolate the organisms (mostly bacteria) from a mixed population into a pure culture. The inoculum is streaked over the agar surface to “thin out” the bacteria. Some individual bacterial cells are separated and well-spaced from each other.

By streaking, a dilution gradient is established across the surface of the agar plate. Because of this, confluent growth occurs on the part of the plate where the bacterial cells are not sufficiently separated; in other regions where few bacteria are deposited, separate macroscopic colonies develop. Each well-isolated colony is assumed to arise from a single bacterium and represent a clone of a pure culture.