Final answer:
When the number of colonies is too great, subcultures have to be made from liquid culture onto the plate, using methods such as the streak plate method to create colonies and achieve a pure culture.
Step-by-step explanation:
When the number of colonies is too great, subcultures have to be made from liquid culture onto the plate. The goal is to separate bacteria in a mixed culture and isolate a single type of bacteria from a source that contains many.
This can be achieved through methods such as the streak plate method, where the cells are diluted by spreading them over the surface of an agar plate to create colonies.
These colonies represent the descendants of a single bacterial cell and provide a pure culture with only one type of bacteria.